Clark Kerr v. M killian/az Dept of Revenue , 207 Ariz. 181 ( 2004 )


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  •                     SUPREME COURT OF ARIZONA
    En Banc
    CLARK J. KERR and BILLIE SUE      )   Arizona Supreme Court
    KERR, husband and wife, SUSAN     )   No. CV-03-0110-PR
    MORAN, STEVE ALLEN and JOHN       )
    UDALL, individually and as        )   Court of Appeals
    representatives of the class      )   Division One
    comprised of federal employees    )   No. 1 CA-TX 00-0023
    who paid Arizona income taxes on  )
    federal retirement contributions  )   Arizona   Tax Court
    during one or more of the years   )   Nos. TX   97-00119
    1984 to date,                     )        TX   97-00131
    )        TX   97-00150
    Plaintiffs-Appellees, )
    Cross-Appellants, )
    )   O P I N I O N
    v.               )
    )
    MARK J. KILLIAN, in his capacity )
    as Director of the Arizona        )
    Department of Revenue, the        )
    ARIZONA DEPARTMENT OF REVENUE OF )
    THE STATE OF ARIZONA,             )
    )
    Defendants-Appellants, )
    Cross-Appellees. )
    __________________________________)
    )
    STATE OF ARIZONA ex rel., the     )
    ARIZONA DEPARTMENT OF REVENUE,    )
    )
    Plaintiff-Appellant, )
    Cross-Appellee, )
    )
    v.               )
    )
    CLARK J. KERR and BILLIE SUE      )
    KERR, husband and wife,           )
    )
    Defendants-Appellees, )
    Cross-Appellants. )
    __________________________________)
    )
    CLARK J. KERR and BILLIE SUE      )
    KERR, husband and wife; and       )
    their ATTORNEYS, BONN, LUSCHER,   )
    PADDEN & WILKINS, CHARTERED and   )
    O'NEIL, CANNON & HOLLMAN, S.C.,   )
    )
    Counterclaimants-Appellees, )
    Cross-Appellants, )
    )
    v.               )
    )
    STATE OF ARIZONA ex rel., the     )
    ARIZONA DEPARTMENT OF REVENUE,    )
    )
    Counterdefendant-Appellant, )
    Cross-Appellee. )
    )
    __________________________________)
    Appeal from the Superior Court of Maricopa County
    Arizona Tax Court
    The Honorable William J. Schafer, III, Judge
    The Honorable Susan R. Bolton, Judge
    REVERSED IN PART AND REMANDED
    Opinion of the Court of Appeals, Division One
    
    204 Ariz. 485
    , 
    65 P.3d 434
    VACATED IN PART
    BONN & WILKINS, CHARTERED                                   Phoenix
    By: Paul V. Bonn
    Randall D. Wilkins
    D. Michael Hall
    Brian A. Luscher
    and
    O’NEIL, CANNON & HOLLMAN, S.C.                      Milwaukee, WI
    By: Eugene O. Duffy
    Attorneys for Appellees, Cross-Appellants
    TERRY GODDARD, ATTORNEY GENERAL                             Phoenix
    By: Michael P. Worley
    Attorneys for Appellant, Cross-Appellee
    2
    H U R W I T Z, Justice
    ¶1         The question in this case is whether Arizona’s income
    tax scheme violates the intergovernmental tax immunity doctrine
    because   it    effectively    subjects   federal     employees’      mandatory
    retirement     contributions   to   current    taxation,      while   deferring
    taxation of similar contributions by state and local employees.
    We conclude that the state income tax code does not discriminate
    against federal employees because of the source of their pay or
    compensation, and thus does not violate the intergovernmental
    tax immunity doctrine, codified in 4 U.S.C. § 111(a) (2000).
    I.
    ¶2         This case has a long and complicated procedural and
    substantive history.     This litigation commenced in 1989 and has
    been the subject of five prior reported appellate opinions.1                 We
    begin with a review of the “long strange trip”2 that brought this
    case here.
    1
    See Kerr v. Killian, 
    204 Ariz. 485
    , 
    65 P.3d 434
    (App.
    2003) (“Kerr V”); Kerr v. Killian, 
    201 Ariz. 125
    , 
    32 P.3d 408
    (App. 2001) (“Kerr IV”); Kerr v. Killian, 
    197 Ariz. 213
    , 
    3 P.3d 1133
    (App. 2000) (“Kerr III”); Kerr v. Waddell, 
    185 Ariz. 457
    ,
    
    916 P.2d 1173
    (App. 1996) (“Kerr II”); Kerr v. Waddell, 
    183 Ariz. 1
    , 
    899 P.2d 162
    (App. 1994) (“Kerr I”). We refer in this
    opinion to these previous opinions by the parenthetical
    shorthands above.
    2
    Grateful    Dead,    Truckin’,      on   American    Beauty   (Warner
    Bros. 1970).
    3
    A.        The Federal Tax Code
    ¶3            This    controversy         has       its    origins       in    several       arcane
    provisions of the federal tax code.                            Under various sections of
    the   Internal       Revenue    Code,      including            I.R.C.    §§    401    and    403,
    governmental        employers       may    choose         to    establish      “contributory”
    retirement      plans.          A    typical          plan       requires       employees         to
    contribute      a     portion       of     their          income     to       the     plan    (the
    “employee’s      contribution”)           and       the    employer       then       contributes
    additional funds (the “employer’s contribution”).
    ¶4            In the abstract, both the employee’s and employer’s
    contributions would seem to be current taxable income to the
    employee; the former comes out of the employee’s salary, while
    the latter is plainly a benefit conferred by the employer as a
    result   of    the    employee’s          labor.          See    generally          I.R.C.    §   61
    (defining     gross     income       as    “all       income       from       whatever       source
    derived”).      But, in what has aptly been termed “one example of
    the dominance of form over substance in the tax code,” Howell v.
    United States, 
    775 F.2d 887
    , 887 (7th Cir. 1985), federal tax
    law   distinguishes       between         the       employee’s       and       the    employer’s
    contributions.         An employer’s contribution to a retirement plan
    “qualified” under I.R.C. §§ 401(a) and 403(a) is not treated as
    taxable income for the employee until the plan pays benefits to
    the employee.          See 
    Howell, 775 F.2d at 887
    .                             An employee’s
    contribution to a retirement plan, however, is generally treated
    4
    as current taxable income to the employee, even if the employee
    is mandated to make the contributions out of his current pay.
    See   generally   United       States      v.     Basye,    
    410 U.S. 441
    ,    449-50
    (1973)     (treating         contributions            to    retirement         plan     as
    “anticipatory     assignments         of     income”).       The    employee     is    not
    taxed,    however,     on    the     eventual     distributions         from   the    plan
    corresponding to his taxable contributions.                    See I.R.C. § 72.
    ¶5          In 1974, Congress complicated the situation further by
    enacting Pub. L. No. 93-406, 88 Stat. 825 (1974), codified at
    I.R.C. § 414(h)(2).           Section 414(h)(2) provides that if a state
    or local governmental employer “picks up” employee contributions
    to    a   plan    qualified          under       §§   401(a)       or   403(a),       “the
    contributions     so        picked    up     shall     be   treated       as    employer
    contributions,” and thus not subjected to current income tax.
    The Internal Revenue Service has established two criteria that
    must be met before a state or local government can “pick up”
    employee contributions:
    First,   the    employer   must    specify    that   the
    contributions,    although   designated    as   employee
    contributions, are being paid by the employer in lieu
    of contributions by the employee.           Second, the
    employee must not have the option of choosing to
    receive the contributed amounts directly instead of
    having them paid by the employer to the pension plan.
    Rev. Rul. 81-35, 1981-1 C.B. 255.
    5
    B.      Arizona’s Income Tax Scheme
    ¶6           In 1979, Arizona adopted federal adjusted gross income
    (“AGI”)     as    the    starting       point       for   computing            Arizona         taxable
    income.      1978       Ariz.     Sess.       Laws,    ch.      213,       §    2    (codified      as
    amended     at    Arizona       Revised       Statutes         (“A.R.S.”)            §    43-1001(2)
    (Supp. 2003) (“‘Arizona gross income’ of a resident individual
    means the individual’s federal adjusted gross income for the
    taxable     year,       computed        pursuant          to     the       internal            revenue
    code.”)).         The    income     tax       statutes         list    a       series      of    items
    Arizona taxpayers must add to, or may subtract from, federal AGI
    to reach their Arizona taxable income.                            See A.R.S. § 43-1021
    (Supp.     2003)   (listing        twenty-seven           additions);               
    id. § 43-1022 (listing
    twenty-nine subtractions).
    ¶7           At the same time that the legislature adopted federal
    AGI   as    the    starting        point       for    calculating              Arizona         taxable
    income, it also amended the state tax code to allow state and
    local      employees         to    subtract           their       mandatory               retirement
    contributions from Arizona gross income.                         1978 Ariz. Sess. Laws,
    ch. 213, § 2 (codified at A.R.S. § 43-1022(2) (Supp. 1978)).
    Under      the     version        of      §     43-1022(2)             adopted            in     1978,
    “[c]ontributions         made      to     the       state      retirement             system,      the
    judges’ retirement fund, the public safety personnel retirement
    system or a county or city retirement plan” could be subtracted
    6
    from        the    employee’s       Arizona        gross     income.3         In    1982,   the
    legislature             added     mandatory        contributions         to    the     elected
    officials’ retirement plan (“EORP”) to the list of subtractions.
    1982 Ariz. Sess. Laws, ch. 126, § 2 (codified at A.R.S. § 43-
    1022(2)           (Supp.    1982)).           In       1986,    contributions         to    the
    corrections officer retirement plan (“CORP”) were added to the
    list.        1986 Ariz. Sess. Laws, ch. 325, § 3 (codified at A.R.S. §
    43-1022(2) (Supp. 1986)).4
    ¶8                In    addition     to   allowing         subtractions        from    Arizona
    taxable           income    of     employee        contributions         to    the     various
    retirement plans, Arizona law also provided until 1989 that all
    benefits paid to employees under those plans could likewise be
    subtracted.             See A.R.S. § 43-1022(3) (Supp. 1988).                      Thus, state
    and local employees could avoid Arizona taxation altogether on
    retirement             benefits,     regardless         of     whether    these       benefits
    derived            from         employers’         contributions          or        employees’
    contributions.             In 1989, however, Davis v. Michigan Department
    of Treasury, 
    489 U.S. 803
    (1989), held that a similar Michigan
    statute violated principles of intergovernmental tax immunity,
    by favoring retired state and local governmental employees over
    3
    We refer in this opinion to the Arizona state
    retirement system as “ASRS” and the public safety personnel
    retirement system as “PSPRS.”
    4
    The same law removed contributions to the judges’
    retirement fund from the list of permitted subtractions, as that
    fund had been combined with EORP. See A.R.S. § 38-802 (2001).
    7
    federal employees, who were not allowed to deduct retirement
    benefits from their taxable Michigan income.
    ¶9                The Arizona legislature promptly reacted to Davis by
    amending A.R.S. § 43-1022(3) to eliminate benefits received from
    state       and    local       retirement     plans          from     the   list    of    permitted
    subtractions            from    Arizona     gross           taxable    income.5          1989    Ariz.
    Sess. Laws, ch. 312, § 12.                    The same statute also removed from
    the list of statutory subtractions contributions to ASRS, EORP,
    and   county         or    city    retirement           plans.          
    Id. In 1991, the
    legislature removed mandatory contributions to CORP and PSPRS
    from its list of subtractions from Arizona gross income.                                          1991
    Ariz.       Sess.       Laws,    ch.   155,     §       8    (retroactively         effective         to
    January 1, 1991).
    ¶10               Thus, for tax years after 1990, Arizona law has not
    provided          for     subtraction         from          gross     income       for    mandatory
    employee contributions to any state or local retirement plans
    and   it     has     treated      benefits      received            from    federal,          state   or
    local plans similarly.                  This did not mean, however, that all
    employee          contributions        were    immediately             subjected         to    current
    Arizona tax.
    5
    At the same time, the legislature amended § 43-1022 to
    allow the annual deduction of up to $2500 of retirement benefits
    received by the taxpayer from either state or federal retirement
    systems. 1989 Ariz. Sess. Laws, ch. 312, § 12 (now codified at
    A.R.S. § 43-1022(2) (Supp. 2003)).
    8
    ¶11         Beginning    in   1985,       the    legislature        had   enacted
    statutes authorizing certain state retirement plans to “pick up”
    employee contributions pursuant to I.R.C. § 414(h)(2).                      1985
    Ariz. Sess. Laws, ch. 294, § 4 (now codified at A.R.S. § 38-
    736(B)    (2001)   (authorizing   ASRS     pick      up));   1985   Ariz.   Sess.
    Laws, ch. 309, § 4 (now codified at A.R.S. § 38-810(E) (2001)
    (authorizing EORP pick up)); 1986 Ariz. Sess. Laws, ch. 325, § 1
    (now codified at A.R.S. § 38-892 (2001) (authorizing CORP pick
    up)).     Prior to 1989, ASRS and EORP had already opted to pick up
    employee     contributions     pursuant         to     §     414(h)(2);     these
    contributions were therefore not included in federal AGI, and
    thus not subject to current Arizona tax, notwithstanding the
    elimination of the previous subtractions in 1989.6
    ¶12         Although CORP had received legislative authorization
    to pick up employee contributions in 1986, it did not elect to
    6
    In addition to the subtractions from income previously
    set forth in A.R.S. § 43-1022(2) for contributions to state
    retirement plans, the statutes governing ASRS and EORP have long
    provided that member contributions “are exempt from state,
    county and municipal taxes.” 1953 Ariz. Sess. Laws, ch. 128, §
    22 (now codified at A.R.S. § 38-792(A) (2001) (ASRS)); 1985
    Ariz. Sess. Laws, ch. 309, § 4 (now codified at A.R.S. § 38-811
    (2001) (EORP)). The same statutes also previously exempted from
    state taxation benefits received from these funds; those
    exemptions were removed in 1989 in the same law that eliminated
    the authorization for subtractions from income. See 1989 Ariz.
    Sess. Laws, ch. 312, § 6 (ASRS); 
    id. § 8 (EORP).
        Presumably,
    the legislature did not remove the exemption of the member
    contributions in 1989 in light of the preexisting pick ups under
    § 414(h)(2) by ASRS and EORP.
    9
    do so immediately; its pick up was first effective on July 1,
    2000.     PSPRS did not receive legislative authorization to pick
    up employee contributions until 1999, 1999 Ariz. Sess. Laws, ch.
    50, § 4; 1999 Ariz. Sess. Laws, ch. 327, § 22 (now codified at
    A.R.S. § 38-843.01 (2001)), and its election was effective at
    the same time as CORP’s.7            Thus, throughout the period from 1989
    to 2000, the thousands of state and local employees covered by
    these     two    plans     paid    current     Arizona      income   tax   on   their
    employee contributions.8
    C.     The § 1983 Action
    ¶13          Respondents are Arizona taxpayers, each of whom was
    employed by the federal government and who paid state income
    taxes on mandatory contributions to federal retirement plans.
    See   Kerr      
    I, 183 Ariz. at 4
    ,    899   P.2d    at   165.     In   1989,
    respondents filed a class action under 42 U.S.C. § 1983 against
    7
    Until 1989, the statutes governing CORP and PSPRS,
    like the statutes then governing ASRS and EORP, provided that
    both benefits received from, and employee contributions to,
    these plans were exempt from state taxation.      A.R.S. § 38-852
    (1985) (PSPRS); A.R.S. § 38-896 (Supp. 1986) (CORP).      In 1989,
    the legislature removed the exemption for benefits from these
    statutes. 1989 Ariz. Sess. Laws, ch. 312, § 9 (PSPRS); 
    id. § 10 (CORP).
      In 1991, the legislature removed the exemption for
    employee contributions from the governing statutes.     1991 Ariz.
    Sess. Laws, ch. 155, § 2 (PSPRS); 
    id. § 6 (CORP).
          8
    As of June 30, 2001, some 26,520 state employees were
    enrolled in PSPRS and CORP. Resp. Sep. App. Tab 9. This number
    was approximately thirteen percent of the total state employee
    population. 
    Id. 10 the Arizona
    Department of Revenue (“ADOR”) and ADOR officials,
    alleging      that   Arizona’s     income    tax   scheme   violated    the
    intergovernmental tax immunity doctrine codified in the Public
    Salary Tax Act of 1939, 4 U.S.C. § 111(a), by treating the
    employee      contributions   of   federal   employees   differently   than
    those of state employees.          Kerr 
    I, 183 Ariz. at 4
    , 899 P.2d at
    165.9       Respondents challenged both former A.R.S. § 43-1022(2),
    under which all employee contributions (even if not picked up by
    employers) could be subtracted from Arizona taxable income, and
    the use in current § 43-1001(2) of federal AGI as the base for
    Arizona taxable income, because it allowed state employees whose
    contributions were picked up to avoid current taxation.           Kerr 
    I, 183 Ariz. at 5
    , 899 P.2d at 166.
    ¶14           The tax court held that the former version of § 43-
    1022(2) violated § 111(a).          
    Id. at 13-14, 899
    P.2d at 174-75.
    It rejected, however, the taxpayers’ attack on § 43-1001(2),
    holding that any disparity resulting from the application of
    I.R.C. § 414(h)(2) to determine federal AGI did not violate the
    intergovernmental tax immunity doctrine.           
    Id. at 14-15, 899
    P.2d
    at 175-76.       The court of appeals affirmed the tax court with
    respect to former § 43-1022(2), 
    id. at 16-17, 899
    P.2d at 177-
    9
    The putative class included respondents and all
    Arizona taxpayers employed by the federal government who paid
    state income tax on their mandatory retirement contributions.
    Kerr 
    I, 183 Ariz. at 4
    , 899 P.2d at 165.
    11
    78, but reversed with respect to § 43-1001(2), holding that the
    effect    of    adopting       federal       AGI    was    to   discriminate         against
    federal employees in favor of state employees whose employers
    had picked up the employee contributions.                         
    Id. at 14-15, 899
    P.2d at 175-76.
    ¶15            After ADOR petitioned for review we vacated Kerr I and
    remanded for reconsideration in light of National Private Truck
    Council,      Inc.     v.   Oklahoma        Tax   Commission,     
    515 U.S. 582
    ,      585
    (1995), which held that before suing under § 1983, plaintiffs
    must    first       exhaust    all    “adequate     remedies.”          On     remand,      the
    court    of     appeals       held    that    these   plaintiffs         had    failed      to
    exhaust their state administrative remedies and remanded to the
    tax court with instructions to dismiss the § 1983 action.                                Kerr
    
    II, 185 Ariz. at 467
    , 916 P.2d at 1183.
    D.      The Refund Suit
    ¶16            At    the    same     time    that   they    instituted         the   §   1983
    action,    respondents         filed    administrative          claims    with       ADOR    on
    behalf of themselves and the class requesting refunds based on
    Arizona’s allegedly unconstitutional tax scheme.                          See Kerr 
    III, 197 Ariz. at 215
    6, 3 P.3d at 1135
    .                       An ADOR hearing officer
    held that the agency had “no legal authority to pass on the
    legality of the statutory scheme or to recognize a class refund
    claim.”       
    Id. Respondents appealed to
    the Board of Tax Appeals
    (“BOTA”), which held that neither ADOR nor BOTA had authority to
    12
    entertain class refund claims.                
    Id. ¶ 7. As
    to respondents’
    individual claims, BOTA held that the adoption of federal AGI in
    § 43-1001(2) did not violate the intergovernmental tax immunity
    doctrine and therefore refused to grant refunds for tax years
    after 1990.       See Kerr 
    IV, 201 Ariz. at 129
    11, 32 P.3d at 412
    .
    BOTA, however, held that those respondents who were parties to
    the    administrative      proceedings      should    be   granted    refunds      for
    taxes paid on their mandatory contributions from 1985 through
    1990.       
    Id. at 128-29 ¶
    11, 32 P.3d at 411-12.10 
                    The governor
    thereafter directed ADOR to make refunds for the tax years from
    1985    to    1990   to   all   taxpayers     who    had   filed   timely    refund
    claims, whether or not they were parties to the administrative
    action.       
    Id. at 129 ¶
    12, 32 P.3d at 412.11
    
    ¶17            Respondents then sought review of the BOTA rulings in
    the tax court.       That court denied respondents’ motion to certify
    a class consisting of “all current and former federal employees
    who    paid    Arizona    income   taxes    on   contributions       they   made   to
    10
    In June 1998, the tax court awarded respondents’
    attorneys twenty percent of each refund as fees.   The court of
    appeals affirmed that award. Kerr 
    III, 197 Ariz. at 220
    , 3 P.3d
    at 1140.
    11
    ADOR later ruled that “taxpayers who were taxed on
    mandatory   retirement    contributions   to   retirement   plans
    maintained by the federal government” for tax years prior to
    1991 and who timely filed amended returns, refund claims, or
    protective claims, were entitled to a refund of excess amounts
    paid in those years.    Ariz. Individual Income Tax Ruling 98-1,
    available at http://www.revenue.state.az.us/rulings/itr98-1.htm.
    13
    United   States      Government       retirement       plans     from   1984     to   the
    present who have not received refunds of such taxes.”                          Kerr 
    IV, 201 Ariz. at 129
    13, 32 P.3d at 412
    .                     The court also denied
    the taxpayers’ “alternative motion to certify a class of all
    federal employees who filed timely refund claims for one or more
    years from 1991 to the present.”                 
    Id. The tax court,
    however,
    held that the use of federal AGI as the Arizona tax base in §
    43-1001(2)     violated         §    111(a)     because     its    effect      was     to
    discriminate      against       federal       employees     in     favor    of    state
    employees.     
    Id. ADOR appealed and
    respondents cross-appealed.
    ¶18         In Kerr IV, concluding the reasoning of Kerr I was
    “incomplete and ultimately 
    incorrect,” 201 Ariz. at 130
    18, 32 P.3d at 413
    , the court of appeals rejected respondents’ attack
    on § 43-1001(2) and thus rejected any claims for refunds for tax
    years after 1990.          
    Id. at 131 ¶
    22, 32 P.3d at 414
    .                 The court
    held that the Arizona taxing scheme did not violate § 111(a),
    because it did not discriminate “‘because of the [federal or
    state] source of pay or compensation.’”                   
    Id. (quoting 4 U.S.C.
    §
    111(a)).        Kerr       IV       concluded     that     the     Arizona       scheme
    “distinguishes       not   between      state    and     federal    employees,        but
    rather between all those whose employers make or pick up their
    mandatory contributions and all those whose employers do not.”
    
    Id. ¶ 26. 14
    ¶19          With respect to tax years 1985 through 1990, Kerr IV
    affirmed     the     tax      court’s          conclusion      that   certification          of    a
    class of those whose refund claims had been denied would be
    redundant and unnecessary.                     
    Id. at 133 ¶¶
    33-34, 32 P.3d at 416
    .
    As to those in the putative class who had not filed written
    refund    claims,         relying         on    Arizona     Department        of    Revenue       v.
    Dougherty, 
    198 Ariz. 1
    , 
    6 P.3d 306
    (App. 2000) (“Ladewig I”),
    the court of appeals held that the tax court acted within its
    discretion in denying class status to those taxpayers who had
    failed to exhaust applicable statutory administrative remedies.
    Kerr 
    IV, 201 Ariz. at 133
    35, 32 P.3d at 416
    .
    ¶20          Shortly after the court of appeals issued Kerr IV, we
    held in Arizona Department of Revenue v. Dougherty, 
    200 Ariz. 515
    , 
    29 P.3d 862
    (2001) (“Ladewig II”), that a class action can
    be    used      as   a    vehicle         for     bringing      and   exhausting         certain
    administrative             claims.                Respondents         then         moved      for
    reconsideration          of    the    class       action       rulings   in    Kerr     IV   with
    respect to tax years 1985 through 1990 in light of Ladewig II;
    they     also     sought      reconsideration             of    the   court        of   appeals’
    substantive rejection of their claims with respect to tax years
    after 1990.
    ¶21          The         court       of        appeals     granted       the       motion     for
    reconsideration and issued the opinion now under review, Kerr V,
    
    204 Ariz. 485
    , 
    65 P.3d 434
    .                       In Kerr V, the court of appeals
    15
    held that its analysis in Kerr IV rested on a “narrow, mistaken
    application of the literal language of 4 U.S.C. § 111.”                       
    Id. at 491 ¶
    23, 65 P.3d at 440
    .            Because the effect of § 43-1001(2)
    for tax years after 1990 was to require federal employees to pay
    current     Arizona   income   tax   on      their   mandatory     contributions,
    while deferring such taxation for state and local employees, the
    court of appeals held that United States Supreme Court case law
    interpreting § 111(a) mandated that the Arizona scheme be struck
    down    unless   it   was   justified     by    “‘significant       differences’”
    between these classes.         
    Id. (quoting Davis, 489
    U.S. at 815-16).
    Finding none, Kerr V concluded that § 43-1001(2) violated the
    intergovernmental tax immunity doctrine.                  
    Id. at 493-95 ¶¶
    28-
    
    37, 65 P.3d at 442-44
    .         As to class action issues, the court of
    appeals determined that it was best to allow the tax court “a
    fresh look” in light of Ladewig II, and remanded to the tax
    court for reconsideration of these issues.                  
    Id. at 496-97 ¶
    46,
    65 P.3d at 445-46
    .
    ¶22          ADOR     petitioned        for      review         only     on      the
    intergovernmental tax immunity issue.                We granted review because
    of    the   obvious   statewide   importance         of   the   issue.    We    have
    jurisdiction pursuant to Article 6, Section 5(3) of the Arizona
    Constitution, Arizona Rule of Civil Appellate Procedure 23, and
    A.R.S. § 12-120.24 (2003).
    16
    II.
    ¶23         The    intergovernmental         tax    immunity   doctrine       has    its
    genesis in M’Culloch v. Maryland, 17 U.S. (4 Wheat.) 316 (1819),
    which held that Maryland could not impose a tax on the Bank of
    the United States.       See 
    Davis, 489 U.S. at 810
    .              Until 1938, the
    doctrine     was   expansively      interpreted        to    prohibit    state       and
    federal    governments       from   taxing     the    salaries    of    the    other’s
    employees.        See Jefferson County v. Acker, 
    527 U.S. 423
    , 436
    (1999), and cases cited therein.
    ¶24          In the late 1930s, however, the doctrine underwent a
    significant “contraction,” 
    id. at 436 n.6,
    at the hands of the
    Supreme Court.       First, in Helvering v. Gerhardt, 
    304 U.S. 405
    (1938), the Court held that the federal government could tax the
    salaries of employees of the Port of New York Authority.                            Then,
    in Graves v. New York ex rel. O’Keefe, 
    306 U.S. 466
    (1939), the
    Court expressly overruled a number of prior decisions and held
    that a state’s imposition of an income tax on the salaries of
    federal    employees     placed     no   unconstitutional         burden       on    the
    federal    government.         Since     Graves,       the   Supreme     Court       has
    proclaimed    “a    narrow    approach    to       governmental   tax    immunity.”
    United States v. New Mexico, 
    455 U.S. 720
    , 735 (1982).                        Case law
    after Graves has made plain that the doctrine “barred only those
    taxes that were imposed directly on one sovereign by the other
    17
    or that discriminated against a sovereign or those with whom it
    dealt.”    
    Davis, 489 U.S. at 811
    .
    ¶25            In its decisions contracting the intergovernmental tax
    immunity doctrine, the Supreme Court has “recognized that the
    area      is        one     over         which        Congress       is    the      principal
    superintendent.”             Jefferson 
    County, 527 U.S. at 425
    .                         Shortly
    after Graves was announced, Congress adopted the Public Salary
    Tax Act of 1939, “the primary purpose of which was to impose
    federal    income          tax    on    the    salaries       of    all   state    and    local
    governmental         employees.”              
    Davis, 489 U.S. at 810
    .         But,
    “concerned that considerations of fairness demanded equal tax
    treatment       for       state        and    federal     employees,”          Congress      also
    expressly waived in § 4 of the 1939 Act “whatever immunity would
    have otherwise shielded federal employees from nondiscriminatory
    state taxes.”             
    Id. at 812. Section
    4, codified at 4 U.S.C. §
    111(a),    provides          that       “[t]he   United       States      consents      to     the
    taxation       of    pay    or    compensation          for    personal     service       as    an
    officer or employee of the United States,” but only “if the
    taxation does not discriminate against the officer or employee
    because of the source of the pay or compensation.”                                      Section
    111(a)    thus       “codified         the    result     in    Graves,”    and     foreclosed
    subsequent            broader           judicial         interpretation            of          the
    intergovernmental tax immunity doctrine.                             
    Davis, 489 U.S. at 812
    .     The Supreme Court has held that the immunity provided in §
    18
    111(a)     is      “coextensive           with            the     prohibition            against
    discriminatory      taxes           embodied     in       the     modern    constitutional
    doctrine of intergovernmental tax immunity.”                         
    Id. at 813. A.
    ¶26         The    initial          inquiry     under       §     111(a)    is     whether      a
    challenged      state    tax        discriminates         against        federal       employees
    “because of the source” of their compensation.                              If the alleged
    discrimination is not because of the federal source of income,
    but rather for some other reason, there is no violation of the
    intergovernmental tax immunity doctrine.                          See Jefferson 
    County, 527 U.S. at 442-43
    (holding that a facially nondiscriminatory
    Alabama occupational tax exempting those who held licenses under
    other    state     or     county        laws        did     not     violate        §     111(a),
    notwithstanding the fact that the plaintiff federal judges could
    never    qualify        for        exemption,       because        the     tax     “does      not
    discriminate against federal judges in particular, or federal
    officeholders in general, based on the federal source of their
    pay or compensation”); Cheatham v. Eagerton, 
    703 So. 2d 389
    , 391
    (Ala.    Civ.    App.    1997)        (holding      that        exemption    of    state      law
    enforcement officers’ per-diem subsistence allowance from state
    taxation did not violate § 111(a), notwithstanding that federal
    officers     received         no    comparable        allowance,         because        the   tax
    scheme does not discriminate because of the “source” of the pay
    or compensation).
    19
    ¶27         When the state scheme does discriminate because of the
    federal    source      of    pay,    the    cases     require      a    second       level     of
    analysis.        Imposition of a heavier burden on federal employees
    because     of    the       source    of       pay   may      be   justified            only   by
    “significant differences between the two classes.”                                 
    Davis, 489 U.S. at 815-16
    (quoting Phillips Chem. Co. v. Dumas Indep. Sch.
    Dist., 
    361 U.S. 376
    , 383 (1960)).                    In determining whether this
    standard    of     justification           is    met,      decisions         in    the     equal
    protection field “are not necessarily controlling.”                               
    Id. at 816. Rather,
    the inquiry is whether the inconsistent tax treatment
    “is    directly        related       to,    and      justified         by,        ‘significant
    differences between the two classes.’”                        Id. (quoting 
    Phillips, 361 U.S. at 383-85
    ).
    B.
    ¶28         The opinion below passed quickly over the first level
    of    analysis    required       under     §    111(a).        The     court       of    appeals
    apparently started from the premise that because the adoption of
    federal    AGI    as    the    Arizona      income      tax    base     in    §     43-1001(2)
    effectively required respondents to pay current tax on their
    employee contributions while deferring taxation for state and
    local employees whose contributions had been picked up under
    I.R.C. § 414(h)(2), the Arizona scheme necessarily discriminated
    against respondents because of the federal source of their pay.
    Kerr 
    V, 204 Ariz. at 440-41
    24, 65 P.3d at 491-92
    .
    20
    ¶29           We reach a contrary conclusion.                  At the outset, it is
    worth     noting      that    every      Supreme     Court      decision     cited    by
    respondents in which a state tax was found to violate § 111(a)
    or the intergovernmental tax immunity doctrine involved a tax
    statute       which    discriminated        on     its     face    against     federal
    employees or federal property.                 For example, in Davis, Michigan
    law provided a deduction for retirement benefits paid by the
    state or its political subdivisions, but not for benefits paid
    by others, including the federal government.                      
    Davis, 489 U.S. at 805
    ; 
    id. at 814 (“It
    is undisputed that Michigan’s tax system
    discriminates in favor of retired state employees and against
    retired federal employees.”).               Similarly, the Kansas tax scheme
    struck down in Barker v. Kansas, 
    503 U.S. 594
    (1992), provided a
    statutory deduction for benefits received by various state and
    federal       retirees,      but    no   deduction       for   military    retirement
    benefits.       
    Id. at 596. And,
    the Texas scheme invalidated in
    Phillips      expressly      treated     lessees    of    state    land    differently
    than other lessees, including lessees of federal 
    property. 361 U.S. at 379-80
    .           Thus, each of these cases quickly concluded
    that    the    challenged      tax    scheme     discriminated      because    of    the
    federal source of pay, and focused almost exclusively on whether
    such    discrimination        was    justified     by     significant      differences
    between the disadvantaged federal plaintiffs and the advantaged
    class.
    21
    ¶30           In     contrast,          §     43-1001(2)            contains      no    overt
    discrimination against any taxpayer because of the source of
    pay.        Every Arizona taxpayer, whether employed by the federal
    government, the State, a political subdivision, or a private
    employer,      begins     with    federal         AGI   as    the    Arizona      income    tax
    base.       And, in contrast to the situation that obtained for tax
    years       before    1991,       Arizona         law    no     longer      provides        for
    subtraction        from   that     base       of     contributions         made    by   state
    employees, while denying such subtraction to federal employees.
    ¶31           Respondents        have       not     identified       any   Supreme      Court
    decision in which a facially neutral state tax scheme was found
    to have violated the intergovernmental tax immunity doctrine.
    Respondents’ citation to Memphis Bank & Trust Co. v. Garner, 
    459 U.S. 392
    (1983), as an example of such a case is unavailing.12
    The Tennessee business tax at issue in Memphis Bank, like the
    Arizona income tax code, started with a federal AGI base.                                   
    Id. at 394 &
    n.3.         But a Tennessee statute then added to the base
    all     income     derived       from       obligations       of     states    other       than
    12
    Memphis Bank did not involve an income tax, and thus
    did not interpret § 111(a). Rather, the statute involved was 31
    U.S.C. § 742, which allows nondiscriminatory franchise or other
    non-property taxes to be imposed on federal obligations or
    interest therefrom. Memphis 
    Bank, 459 U.S. at 395-96
    . However,
    because § 742, like § 111(a), is a “restatement of the
    constitutional rule” of intergovernmental tax immunity, the
    analysis under each section is functionally the same.    
    Id. at 396-97. 22
    Tennessee.            
    Id. Because federal AGI
          already     included
    obligations        of     the    United     States,        see   I.R.C.     §    103,      the
    Tennessee law thus provided an express exemption from taxation
    for    income      from   bonds       issued   by   Tennessee      and    its    political
    subdivisions,         while     taxing     similar    obligations         issued      by   the
    United       States     and     all    other    states.          
    Id. The Tennessee statutory
    scheme thus expressly differentiated between interest
    received on that state’s obligations and all other obligations,
    including those of the federal government.13
    ¶32           Respondents        argue     that     even    if   there    is     no    facial
    discrimination in § 43-1001(2), we must examine the “practical
    operation” of the Arizona scheme.                     See 
    Phillips, 361 U.S. at 383
    .        We agree.         If the inevitable consequence of a facially
    neutral state tax code were that federal employees were taxed
    differently than similarly situated state employees because of
    the source of their income, or if the distinctions drawn in the
    state       code   were       “only    a   cloak     for     discrimination           against
    federally funded [pay or compensation],” 
    Barker, 503 U.S. at 604-05
    , § 111(a) would plainly invalidate such a scheme.                                   But
    this is not such a case.               In “practical operation,” § 43-1001(2)
    does not require that federal employees be taxed differently
    13
    Kraft General Foods, Inc. v. Iowa Department of
    Revenue, 
    505 U.S. 71
    (1992), upon which respondents also rely,
    is even further afield.       That case did not interpret the
    intergovernmental tax immunity doctrine, but rather the Foreign
    Commerce Clause, U.S. Const. art. 1, § 8, cl. 3.
    23
    than    state    employees       with     respect     to      mandatory       retirement
    contributions.          Arizona      taxes   the    employee        contributions       of
    those state employees whose contributions have not been picked
    up by their employers in precisely the same fashion as it treats
    the employee contributions of federal employees.
    ¶33           The distinction is not simply theoretical; it has had
    real practical effects on Arizona taxpayers.                         As noted above,
    from 1990 through 2000, the majority of the tax years covered by
    this litigation, the employee contributions of the thousands of
    state and local employees covered by PSPRS and CORP were not
    picked up, and each of these employees therefore paid current
    state   tax     on    those    contributions.            While   the      treatment     of
    numerous state and local employees in a fashion identical to the
    allegedly       disadvantaged        federal       employees        may      not   itself
    conclusively         prove    that   a   state     scheme     does     not    violate    §
    111(a), it surely demonstrates that the Arizona scheme is not
    simply a “cloak for discrimination.”
    ¶34           More     importantly,       nothing        in   the    Arizona       scheme
    discriminates between taxpayers based on the federal or non-
    federal source of income; the distinction is instead based on
    whether a particular governmental employer has voluntarily opted
    to pick up the employee contributions and treat them as employer
    contributions.           Section     414(h)(2)      is     permissive;        it   treats
    employee contributions as employer contributions for federal tax
    24
    purposes     only    if    the    employer       voluntarily           opts   for       such
    treatment.
    ¶35        Respondents          argue    that        because     §     414(h)(2)        only
    authorizes state and local governmental employers to pick up
    employee     contributions,       the    effective        distinction         in    §   43-
    1001(2) between those employers who pick up and those who do not
    necessarily     discriminates          against       federal     employees.             This
    argument, however, takes far too narrow a view of the national
    government    and    the   choices      it     has    made.       Section       414(h)(2)
    simply gave state and local employers the option to choose to
    pick up; without advance federal authorization, they could never
    choose to do so.          The federal government, however, already had
    that option and, through its legislative branch, can exercise
    that option at any time it desires.                    In “practical operation,”
    the federal government has thus far simply voluntarily opted not
    to pick up, just as some state employers voluntarily so opted in
    Arizona throughout the 1990s.             Once the state employers made the
    choice to pick up, their employees’ contributions were treated
    identically     to     those      of    governmental            employers       who     had
    previously made this election.               When and if the federal employer
    makes the same choice, Arizona tax law will treat its employees’
    contributions in an identical fashion.
    ¶36        In    short,     §     43-1001(2)         is   not    a     subterfuge        for
    discrimination       against     respondents         because      of    their      federal
    25
    source    of     pay,    nor    is     Arizona’s       treatment    of     respondents’
    employee contributions a necessary consequence of their federal
    status.       Rather, the difference is not who pays the employees,
    but the voluntary choice made by the employer as to whether the
    contributions should be picked up.
    ¶37           Cases     dealing      with    military       retirement     benefits   are
    particularly instructive on this point.                        Barker invalidated a
    Kansas     tax       scheme     which       allowed        subtraction      of   various
    retirement       benefits,       both       state    and     federal,     from   taxable
    income, because the statutes did not permit benefits received by
    retired federal military personnel to be deducted.                          Barker, 
    503 U.S. 594
    .        In contrast, Cooper v. Commissioner of Revenue, 
    658 N.E.2d 963
    (Mass. 1995), decided some three years after Barker,
    upheld    a    Massachusetts         statutory       scheme    which      exempted    from
    taxation       retirement       benefits         received    from   any    governmental
    pension       fund      to     which       the      taxpayer    contributed       during
    employment, while taxing benefits received from all other plans.
    The    federal       military     retirement         pension    system     involved    no
    employee      contributions,         and     all    military    retirees      were    thus
    subjected to Massachusetts income tax on their benefits.                         
    Id. at 964. The
    “practical operation” of the Massachusetts plan, at
    least with respect to military retirees, was thus identical to
    the Kansas scheme.            Nonetheless, Cooper held that any differing
    treatment of military retirees from other government retirees in
    26
    Massachusetts was not because of the “source of pay,” but rather
    because the federal government had designed their plan as non-
    contributory.           
    Id. Because all non-contributory
          plans       were
    treated     equally      —    even    though        virtually     all     Massachusetts
    employees       now     participated         in     contributory        plans14    —     any
    differing       treatment       was   not     because       of   the    source     of    the
    military retirees’ income, but rather because of a separate,
    non-pretextual, distinction.                Id.15
    ¶38         The same is true here.                   Arizona tax law effectively
    distinguishes         between    taxpayers          whose    governmental     employers
    choose     to    pick    up     employee       contributions       and     those       whose
    governmental employers do not choose to do so.                         That distinction
    is not “because of the source” of the employee’s compensation
    14
    Massachusetts established its contributory retirement
    system in 1936 and 1937. 
    Cooper, 658 N.E.2d at 965
    . Thus, it
    was doubtful that any current state retiree participated in a
    non-contributory system, although the Supreme Judicial Court so
    assumed for purposes of analysis in Cooper.      Cf. Filios v.
    Comm’r of Rev., 
    615 N.E.2d 933
    , 936 (Mass. 1993) (noting
    theoretical possibility that state employee participants in old
    non-contributory plans were still alive).
    15
    Respondents argue that Cooper is no longer good
    authority because the Massachusetts legislature has since
    changed the statutory tax scheme to exempt military retirement
    pay from state taxation.   See Mass. 1987 Legis. Serv., ch. 139
    (amending Mass. Gen. Laws Ann. ch. 62, § 2(a)(2)(E)).       But
    nothing in the federal governmental tax immunity doctrine
    prevents a state from exchanging one non-discriminatory scheme
    for another, and we do not ordinarily infer any invalidity in a
    statute from subsequent legislative amendment.
    27
    and therefore does not run afoul of the intergovernmental tax
    immunity doctrine.16
    III.
    ¶39          For   the   reasons   above,   we    hold    that   the   court    of
    appeals erred in Kerr V in concluding that the application of §
    43-1001(2)    to   respondents     violated      the    intergovernmental      tax
    immunity doctrine codified in § 111(a).                We therefore vacate the
    opinion below insofar as it so held and reverse the judgment of
    the tax court to the same extent.                Because ADOR did not seek
    review of that portion of the opinion below remanding the class
    certification issue with respect to tax years 1985 through 1990
    to the tax court for further consideration in light of Ladewig
    II, we do not address that portion of the opinion below.17                  This
    16
    Because we conclude that use of federal AGI as the
    Arizona tax base in § 43-1001(2) does not violate the
    intergovernmental tax immunity doctrine, we do not need to
    consider whether in this case any discrimination is justified by
    substantial   differences    between   respondents   and   state
    governmental employees.   Cf. Witte v. Dir. of Rev., 
    829 S.W.2d 436
    (Mo. 1992) (upholding Missouri tax scheme which imposed
    current taxation on employee contributions to federal Civil
    Service Retirement System, while deferring taxation to other
    retirement plans, because of plaintiffs’ failure to show a lack
    of significant differences between the two classes).
    17
    Our disposition of the intergovernmental tax immunity
    issue moots any question as to whether class certification
    should have been granted with respect to claims relating to tax
    years after 1990.
    28
    case       is   remanded   to   the   tax    court   for   further   proceedings
    consistent with this opinion.
    Andrew D. Hurwitz, Justice
    CONCURRING:
    _
    Charles E. Jones, Chief Justice
    ______
    Ruth V. McGregor, Vice Chief Justice
    _
    Michael D. Ryan, Justice
    _
    John Pelander, Judge*
    *
    The Honorable Rebecca White Berch recused herself; pursuant
    to Article VI, Section 3 of the Arizona Constitution, the
    Honorable John Pelander, Judge of the Court of Appeals, Division
    Two, was designated to sit in her stead.
    29