Scope of the Definition of "Variola Virus" Under the Intelligence Reform and Terrorism Prevention Act of 2004 ( 2008 )


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  •                   Scope of the Definition of “Variola Virus”
    Under the Intelligence Reform and
    Terrorism Prevention Act of 2004
    The definition of “variola virus” in 18 U.S.C. § 175c does not include other naturally occurring
    orthopoxviruses, such as cowpox and vaccinia, but is rather limited to viruses that cause smallpox or
    are engineered, synthesized, or otherwise produced by human manipulation from the variola major
    virus or its components.
    July 24, 2008
    MEMORANDUM OPINION FOR THE ACTING GENERAL COUNSEL
    DEPARTMENT OF HEALTH AND HUMAN SERVICES
    Section 6906 of the Intelligence Reform and Terrorism Prevention Act of 2004,
    Pub. L. No. 108-458, 118 Stat. 3638, 3773 (“the Act” or “IRTPA”), makes it a
    criminal offense for “any person to knowingly produce, engineer, synthesize,
    acquire, transfer directly or indirectly, receive, possess, import, export, or use, or
    possess and threaten to use, variola virus,” 18 U.S.C. § 175c(a)(1) (Supp. V 2005),
    but exempts “conduct by, or under the authority of, the Secretary of Health and
    Human Services,” 
    id. § 175c(a)(2).
    The statute defines “variola virus” as “a virus
    that can cause human smallpox or any derivative of the variola major virus that
    contains more than 85 percent of the gene sequence of the variola major virus or
    the variola minor virus.” 
    Id. § 175c(d).
    Violations are punishable by fines of up to
    $2,000,000 and imprisonment for 25 years to life. See 
    id. § 175c(c)(1).
       You have requested our opinion regarding the scope of the statutory definition
    of “variola virus.” Specifically, you ask whether that definition encompasses other
    viruses in the orthopoxvirus genus, such as cowpox and vaccinia, that occur
    naturally, generally affect animals rather than humans, and are commonly used in
    medical and veterinary research, including the development of smallpox vaccines.
    For the reasons set forth below, we conclude that section 175c does not apply to
    such orthopoxviruses, but rather only to viruses that cause smallpox or are
    engineered, synthesized, or otherwise produced by human manipulation from the
    variola major virus or its components. 1
    I.
    The variola major and minor viruses cause smallpox, a highly contagious and
    often fatal disease. Smallpox is classified by the Centers for Disease Control and
    1
    In addition to the views of HHS on this question, we have received the views of the National
    Security Division, the Criminal Division, the Department of Homeland Security, the Bureau of Industry
    and Security in the Department of Commerce, and the Department of Agriculture, all of which agree
    with the conclusion we reach in this opinion.
    103
    Opinions of the Office of Legal Counsel in Volume 32
    Prevention (“CDC”) as a “Category A” bioterrorism agent or disease. 2 Although
    the World Health Organization declared in 1980 that smallpox had been eradicated
    worldwide, the United States and Russia maintain official government repositories
    of the variola virus for research purposes. The Department of Health and Human
    Services (“HHS”) conducts and supports research on countermeasures to small-
    pox. This research involves not only the variola virus itself, but also other closely
    related orthopoxviruses including cowpox (which Dr. Edward Jenner discovered
    in the 1790s could be used as a vaccine against smallpox), vaccinia (a similar virus
    later used to make smallpox vaccine), camelpox, and monkeypox. Although
    humans may be infected by animal orthopoxviruses, most of these viruses have
    milder effects on humans than smallpox and are significantly less contagious. 3
    Your concern is that the statutory definition of “variola virus,” specifically the
    phrase “any derivative of the variola major virus that contains more than 85
    percent of the gene sequence of the variola major virus or the variola minor virus,”
    might be interpreted to prohibit research involving these other orthopoxviruses.
    The statute does not define the term “derivative.” You believe that this term
    should be interpreted as referring only to viruses engineered or otherwise created
    by human manipulation of the variola virus, but you are concerned that it might be
    read more broadly to include viruses that have been “deriv[ed]” naturally through
    evolution (although you suggest that scientists in this field do not usually use the
    term “derivative” in this sense). You have informed us that there is at present no
    scientific consensus regarding whether the variola virus and other orthopoxviruses
    evolved from a common genetic ancestor or whether variola or one of the other
    orthopoxviruses might be the ancestor of others. See, e.g., I.V. Babkin et al.,
    Analysis of Nucleotide Sequences of Individual Orthopoxvirus Genes (World
    Health Organization 2003) (abstract available at http://www.who.int/csr/disease/
    smallpox/abstracts2003/en) (last visited Aug. 15, 2014) (noting that “[t]he evolu-
    tionary relationships of various orthopoxvirus species are far from being clarified,”
    and arguing that “cowpox or cowpox-like virus was the ancestor of all the modern
    2
    The CDC defines “Category A” “Bioterrorism Agents/Diseases” as those that “pose a risk to
    national security” because they
    • can be easily disseminated or transmitted from person to person;
    • result in high mortality rates and have the potential for major public health impact;
    • might cause public panic and social disruption; and
    • require special action for public health preparedness.
    See http://www.bt.cdc.gov/agent/agentlist-category.asp (last visited Aug. 15, 2014).
    3
    We note that monkeypox may pose a greater threat than other animal orthopoxviruses and in fact
    has caused human deaths in Africa, but we understand that it is significantly less infectious and less
    likely to be fatal than smallpox. The CDC does not list monkeypox as a Category A, B, or C
    bioterrorism agent, see http://www.bt.cdc.gov/agent/agentlist.asp (last visited Aug. 15. 2014), but it
    does include monkeypox in its list of “select agents,” which “have the potential to pose a severe threat
    to public health and safety,” 42 C.F.R. § 73.3 (2007). Unauthorized possession or transfer of
    monkeypox virus is thus subject to criminal penalties under 18 U.S.C. § 175b (Supp. V 2005).
    104
    Scope of the Definition of “Variola Virus” Under the IRTPA of 2004
    orthopoxviruses”). If one or more of the other orthopoxviruses were subsequently
    found to have evolved from variola major virus, however, they would be subject to
    the statute’s criminal prohibitions under the broader reading. You also indicate
    that there is no scientific consensus concerning the correct interpretation of
    quantitative data regarding the gene sequence homology of related viruses, but
    note that, under at least one approach, other orthopoxviruses might be found to
    contain more than 85 percent of the variola major or minor gene sequence.
    Because of these unresolved questions, you are concerned that important and
    beneficial scientific research involving non-variola orthopoxviruses may be chilled
    by fear of criminal liability. 4
    II.
    A.
    In addressing this question, we must begin with the language of the statute. The
    first part of the variola virus definition—“a virus that can cause human small-
    pox”—raises no question of interpretation and does not concern us here. We need
    address only the second, alternative definition—“any derivative of the variola
    major virus that contains more than 85 percent of the gene sequence of the variola
    major virus or the variola minor virus.” This second definition itself has two parts:
    the virus must be “a derivative of the variola major virus” and it must also
    “contain[] more than 85 percent of the gene sequence of the variola major virus or
    the variola minor virus.” Whatever may be meant by “85 percent of the gene
    sequence,” therefore, the second definition can include only those viruses that are
    “derivatives” of the variola major virus. Thus, if other orthopoxviruses are not
    “derivatives” of variola virus within the meaning of the statute, the fact that they
    may contain more than 85 percent of the variola gene sequence is irrelevant for
    purposes of section 175c.
    Because the statute does not define the term “derivative,” we look first to the
    ordinary meaning of that term. See, e.g., Engine Mfrs. Ass’n v. S. Coast Air
    Quality Mgmt. Dist., 
    541 U.S. 246
    , 252 (2004) (“‘Statutory construction must
    begin with the language employed by Congress and the assumption that the
    ordinary meaning of that language accurately expresses the legislative purpose.’”)
    4
    The National Science Advisory Board for Biosecurity (“NSABB”) has recommended that section
    175c be repealed “because current scientific insight precludes meaningful definition of an agent based
    solely on sequence homology . . . . The current definition of variola virus, as provided in the statute,
    could be interpreted to include other less harmful naturally occurring poxviruses such as vaccinia virus
    that are vital to beneficial research, thereby inadvertently restricting and potentially making criminal
    many types of beneficial research such as the development and production of smallpox vaccine.”
    NSABB, Addressing Biosecurity Concerns Related to the Synthesis of Select Agents 12 (Dec. 2006)
    (available at http://osp.od.nih.gov/sites/default/files/resources/Final_NSABB_Report_on_Synthetic_
    Genomics.pdf, last visited Aug. 15, 2014).
    105
    Opinions of the Office of Legal Counsel in Volume 32
    (quoting Park ‘N Fly, Inc. v. Dollar Park & Fly, Inc., 
    469 U.S. 189
    , 194 (1985));
    Leocal v. Ashcroft, 
    543 U.S. 1
    , 9 (2004) (“When interpreting a statute, we must
    give words their ‘ordinary or natural’ meaning.”) (quoting Smith v. United States,
    
    508 U.S. 223
    , 228 (1993)). The noun “derivative” has a number of different
    meanings in different fields, but most of the standard dictionaries we have
    examined offer both a general definition and a definition pertaining to chemistry.
    See, e.g., 1 The New Shorter Oxford English Dictionary 641 (1993) (“2. gen.
    Something derived; a thing flowing, proceeding, or originating from another. . . .
    4. Chem. A compound obtained from another by substitution or other simple
    process.”); American Heritage Dictionary of the English Language 489 (4th ed.
    2000) (“1. Something derived. . . . 4. Chemistry A compound derived or obtained
    from another and containing essential elements of the parent substance.”); 
    id. (defining “derive”:
    “1. To obtain or receive from a source. . . . 5. Chemistry To
    produce or obtain (a compound) from another substance by chemical reaction.”);
    Webster’s New International Dictionary 704 (2d ed. 1957) (“one that is derived;
    anything obtained or deduced from another . . . . chem. A substance so related to
    another substance by modification or partial substitution as to be regarded as
    theoretically derived from it, even when not obtainable from it in practice.”);
    Webster’s Third New International Dictionary 608 (1993) (“4. . . . b: a substance
    that can be made from another substance in one or more steps”).
    We also have considered how scientific and medical dictionaries define the
    term “derivative.” See Corning Glass Works v. Brennan, 
    417 U.S. 188
    , 201 (1974)
    (noting that “where Congress has used technical words or terms of art, ‘it (is)
    proper to explain them by reference to the art or science to which they (are)
    appropriate’”) (quoting Greenleaf v. Goodrich, 
    101 U.S. 278
    , 284 (1880)).
    Stedman’s Medical Dictionary defines “derivative” to mean generally “[s]ome-
    thing produced by modification of something preexisting,” or “[s]pecifically, a
    chemical compound that may be produced from another compound of similar
    structure in one or more steps, as in replacement of [a hydrogen atom] by an alkyl,
    acyl, or amino group.” 
    Id. at 461–62
    (26th ed. 2004). See also 1 International
    Dictionary of Medicine and Biology 760 (1986) (“[a] substance derived from
    another by some specific modification of its molecule, usually by substitution or
    addition reactions”); Dorland’s Illustrated Medical Dictionary 478 (29th ed. 2000)
    (“a chemical substance produced from another substance either directly or by
    modification or partial substitution”).
    These dictionary definitions provide some guidance in interpreting the statute,
    although they do not conclusively resolve whether the term “derivative” under
    section 175c includes viruses that may have evolved from or otherwise arisen from
    variola without human involvement. One of the generic definitions—“a thing
    flowing, proceeding, or originating from another”—suggests that derivatives may
    106
    Scope of the Definition of “Variola Virus” Under the IRTPA of 2004
    result from entirely natural processes without human intervention. 5 Most of the
    other definitions, particularly the scientific definitions, imply a more active
    process—describing a “derivative” as a substance arising from “substitution,”
    “modification,” “replacement,” “addition,” or “obtained,” “produced,” or “made”
    in “steps.” And although “substitution,” “modification,” “replacement,” and
    “addition” may result from natural processes, these terms at least suggest deliber-
    ate human intervention. Similarly, while natural processes could “produce” a
    substance in steps, see, e.g., American Heritage Dictionary of the English
    Language 1111 (4th ed. 2004) (defining “produce” as “[t]o bring forth; yield: a
    plant that produces pink flowers”), many uses of that term require human activity,
    see, e.g., 
    id. (defining “produce”
    as “[t]o manufacture”). Finally, in the context of
    creating one entity from another, at least one definition (“a substance that can be
    made from another substance in one or more steps”) unambiguously includes, and
    seems focused on, human intervention. Webster’s Third New International
    Dictionary at 608 (emphasis added).
    Although the dictionary definitions leave some ambiguity regarding whether
    the phrase “derivative of the variola virus” in section 175c(d) implies something
    produced by human activity or more broadly includes any virus that has evolved
    from variola without human interference, we note that the language Congress used
    in section 175c(a)(1) provides some support for the former interpretation. The
    statute prohibits not only the possession or use of variola virus but also “knowing-
    ly produc[ing], engineer[ing], [or] synthesiz[ing] . . . variola virus.” In other
    words, it prohibits knowingly producing, engineering, or synthesizing “any
    derivative of the variola virus.” In that context, the term “derivative” makes
    perfect sense as something produced, engineered, or synthesized by human
    manipulation in a laboratory. Moreover, any violation of the statute must be
    “knowing[].” Since there is currently no known evolutionary descendant of
    variola, there was no reason for Congress to consider whether such a descendant
    should be included in the statutory prohibition or whether any of the animal
    5
    We do not believe that Congress intended to use the term in the sense of something “so related . . .
    as to be regarded as theoretically derived” from another substance, since the statutory definition
    requires both that a virus be a derivative of variola and that it have a close genetic relationship to
    variola. If the statutory definition were satisfied by close relationship alone, the phrase “any derivative
    of the variola major virus” would seem almost redundant. See United States v. Menasche, 
    348 U.S. 528
    , 538–39 (1955) (“It is our duty ‘to give effect, if possible, to every clause and word of a statute.’”)
    (quoting Montclair v. Ramsdell, 
    107 U.S. 147
    , 152 (1883)). Cf. Reckitt & Colman, Ltd. v. Adm’r, DEA,
    
    788 F.2d 22
    , 25–26 (D.C. Cir. 1986) (upholding DEA’s interpretation of the “undefined and potentially
    ambiguous statutory term” “derivative” in the Controlled Substances Act). In Reckitt, the court found
    that DEA had properly determined that a “derivative” of a drug is “any substance (1) prepared from
    that drug, (2) which chemically resembles that drug, and (3) which has some of the adverse effects of
    that drug.” 
    Id. at 24–25.
    The court noted that “[a]lthough the Administrator was not necessarily
    required to follow a strictly scientific definition, . . . the definition he adopted is nevertheless consistent
    with that employed by chemists.” 
    Id. at 25
    (noting that Administrator relied on definition of “deriva-
    tive” in Van Nostrand’s Scientific Encyclopedia (5th ed. 1976) (defining term as expressing “the
    relation between certain known or hypothetical substances and the compound formed from them”)).
    107
    Opinions of the Office of Legal Counsel in Volume 32
    orthopoxviruses might constitute natural “derivatives” of variola. 6 Given the lack
    of any consensus among experts in the field regarding the evolutionary relation-
    ships between smallpox and the animal orthopoxviruses, we are reluctant to
    conclude that Congress intended to impose criminal penalties on the mere
    possession of a class of viruses whose antecedents are currently unknown and
    purely speculative.
    B.
    The proper interpretation of the term “derivative” in section 175c must take
    account also of other provisions of IRTPA. See Koons Buick Pontiac GMC, Inc. v.
    Nigh, 
    543 U.S. 50
    , 60 (2004) (“A provision that may seem ambiguous in isolation
    is often clarified by the remainder of the statutory scheme—because the same
    terminology is used elsewhere in a context that makes its meaning clear, or
    because only one of the permissible meanings produces a substantive effect that is
    compatible with the rest of the law.”) (quotation marks and citation omitted);
    Mastro Plastics Corp. v. NLRB, 
    350 U.S. 270
    , 285 (1956) (“In expounding a
    statute, we must not be guided by a single sentence or member of a sentence, but
    look to the provisions of the whole law, and to its object and policy.”) (citation and
    internal quotation marks omitted). Here, Congress clearly articulated the findings
    and purpose underlying section 6906 within the text of the Act itself. Section
    6902(a) sets forth the following findings with respect to variola virus:
    (3) Variola virus is the causative agent of smallpox, an extremely se-
    rious, contagious, and sometimes fatal disease. Variola virus is clas-
    sified as a Category A agent by the Centers for Disease Control and
    Prevention, meaning that it is believed to pose the greatest potential
    threat for adverse public health impact and has a moderate to high
    potential for large-scale dissemination. . . . Because it is so danger-
    ous, the variola virus may appeal to terrorists.
    (4) The use, or even the threatened use, of . . . the variola virus,
    against the United States, its allies, or its people, poses a grave risk
    to the security, foreign policy, economy, and environment of the
    United States. . . .
    (5) There is no legitimate reason for a private individual or company,
    absent explicit government authorization, to produce, construct, oth-
    6
    Indeed, we do not believe any person currently working with animal orthopoxviruses could be
    subject to prosecution even under the broadest possible reading of the statute. Since no virus has been
    identified as having evolved from variola, there can be no “knowing[]” possession of such an
    evolutionary “derivative” at present.
    108
    Scope of the Definition of “Variola Virus” Under the IRTPA of 2004
    erwise acquire, transfer, receive, possess, import, export, or use . . .
    the variola virus.
    Pub. L. No. 108-458, § 6902, 118 Stat. at 3769, reprinted in 18 U.S.C. § 175c
    note. These statutory findings provide useful guidance in determining Congress’s
    intent in enacting section 175c. Cf. Sutton v. United Air Lines, 
    527 U.S. 471
    , 484,
    487 (1999) (relying on findings enacted as part of the Americans with Disabilities
    Act to interpret statutory term “disability”); Price v. Forrest, 
    173 U.S. 410
    , 427
    (1899) (noting that “preamble may be referred to in order to assist in ascertaining
    the intent and meaning of a statute fairly susceptible of different constructions”).
    In addition, section 6902(b) of the Act states that “[t]he purpose of this subtitle
    [sections 6901–6911 of the Act] is to combat the potential use of weapons that
    have the ability to cause widespread harm to United States persons and the United
    States economy (and that have no legitimate private use) and to threaten or harm
    the national security or foreign relations of the United States.” 7
    The findings and statement of purpose, which are part of the statutory text,
    show that Congress intended to address what it regarded as extremely serious
    threats to national security. While the findings quoted above appear to relate
    only to the variola virus itself, and thus do not specifically address the “any
    derivative” prong of the statutory definition, they support the view that Con-
    gress’s purpose (as stated in section 6902(b)) was to “combat the potential use of
    weapons that have the ability to cause widespread harm . . . and that have no
    legitimate private use.” Vaccinia and other animal orthopoxviruses used in
    research do not fall into either category. They are not classified as Category A
    agents and do not currently “pose[] a grave risk to the security, foreign policy,
    economy, and environment of the United States.” Moreover, we understand that
    there are “legitimate private use[s]” of these non-variola orthopoxviruses in
    medical and scientific research and in the production of smallpox vaccine. 8
    Indeed, Congress has expressly recognized vaccinia as a “covered countermeas-
    ure against smallpox.” 42 U.S.C. § 233(p)(7)(A)(i)(I) (Supp. IV 2004) (authoriz-
    ing the Secretary to exempt manufacturers and health care providers from
    liability for administering the smallpox vaccine). Imposing criminal penalties on
    the possession for legitimate reasons of viruses that do not threaten national
    security would appear to be inconsistent with Congress’s stated purpose. Cf.
    Watt v. Western Nuclear, Inc., 
    462 U.S. 36
    , 56 (1983) (explaining that a statute
    7
    Congress designated title VI, subtitle J, of the Act, which consists of sections 6901 to 6911, as the
    “Prevention of Terrorist Access to Destructive Weapons Act of 2004.” This subtitle also prohibits the
    possession or use of man-portable air defense systems (“MANPADS”), atomic weapons, and
    radiological dispersal devices. Pub. L. No. 108-458, §§ 6903–6905.
    8
    In addition, a broad interpretation of the statute could potentially render unlawful research on
    animal orthopoxviruses conducted by the Department of Agriculture (“USDA”) and its contractors.
    USDA also has statutory authority to regulate and license veterinary vaccines, many of which are based
    on orthopoxviruses. See 21 U.S.C. § 154 (2000).
    109
    Opinions of the Office of Legal Counsel in Volume 32
    should not be interpreted “to produce a result at odds with the purposes underly-
    ing the statute” but rather “in a way that will further Congress’[s] overriding
    objective”).
    There is little legislative history on the variola prohibition, but what there is
    supports the view that Congress intended to criminalize the possession of only
    those “weapons” that pose the most serious threats to national security. In a
    hearing on a predecessor bill containing provisions identical to those later enacted
    as title VI, subtitle J of IRTPA (including the definition of variola), a representa-
    tive of the Justice Department testified that the bill would address “four weapons
    that could be catastrophic in the hands of terrorists”: MANPADS, atomic weap-
    ons, radiological dispersal devices (“dirty bombs”), and the variola virus.
    A Review of the Tools to Fight Terrorism Act: Hearing before the Subcomm. on
    Terrorism, Technology and Homeland Security of the S. Comm. on the Judiciary,
    108th Cong. 7 (2004) (statement of Daniel J. Bryant, Assistant Attorney General).
    The Department noted:
    Current penalties for the unlawful possession of these weapons . . .
    do not adequately reflect the serious threat to public safety and na-
    tional security posed by their enormous destructive power. . . . The
    knowing, unregistered possession of the variola virus has a maxi-
    mum penalty of only 5 years in prison. . . . To provide a much great-
    er deterrent for the possession or use of these weapons, the [bill]
    would establish a zero-tolerance policy toward the unlawful importa-
    tion, possession or transfer of these weapons by imposing very tough
    criminal penalties.
    
    Id. This statement
    suggests that the purpose of the bill was to impose more severe
    penalties on conduct that was already illegal, not to criminalize the possession of
    viruses that fall far short of posing the type of threat posed by MANPADS, atomic
    weapons, radiological dispersal devices, and smallpox. This view was also
    expressed on the Senate floor by Senator Cornyn, who introduced the original bill
    containing these provisions. See 150 Cong. Rec. 25,837 (Dec. 8, 2004) (“Tough
    penalties like these are appropriate for the most dangerous threats our nation faces,
    and that is exactly the kind of threat that these items pose.”). Representative
    Sessions, who introduced the same legislation in the House of Representatives,
    similarly asserted that “weak punishments for the possession or use of these
    weapons [are] simply unacceptable.” 150 Cong. Rec. 22,097 (Oct. 8, 2004).
    Nowhere in the Act or its legislative history did Congress provide any explana-
    tion for its inclusion of the term “derivative” in the definition of “variola virus.”
    We can conceive of at least two possible rationales. First, Congress may have been
    concerned that bioterrorists might modify or engineer the variola virus to produce
    a new deadly virus, immune to smallpox vaccine, that could be used as a terrorist
    110
    Scope of the Definition of “Variola Virus” Under the IRTPA of 2004
    weapon. 9 This theory would support the narrower interpretation of “derivative” as
    something resulting from human manipulation. Alternatively, Congress may have
    been concerned that a virus that had evolved from variola could be engineered
    back into smallpox virus. In that case, however, it would be difficult to explain
    why Congress was not equally or more concerned about the reverse—a predeces-
    sor virus from which variola had evolved—or closely related viruses descended
    from a common ancestor. Moreover, smallpox virus obtained through reverse
    engineering would already be subject to the prohibition on “produc[ing], engi-
    neer[ing], [or] synthesiz[ing] . . . a virus that can cause human smallpox.” We have
    found no support for this alternative theory in the legislative history or text, and
    we think it unlikely that Congress intended to criminalize possession of a currently
    unknown class of viruses without any consideration of the actual danger that might
    be posed by such viruses or the potential impact of such a prohibition on beneficial
    research, including the production of smallpox vaccine. We therefore find that the
    statutory scheme as a whole tends to support the narrower interpretation.
    Finally, a broad interpretation of section 175c may also be in tension with other
    smallpox-related legislation enacted the same year. See Erlenbaugh v. United
    States, 
    409 U.S. 239
    , 244 (1972) (The rule that statutes dealing with the same
    subject should be construed together “necessarily assumes that whenever Congress
    passes a new statute, it acts aware of all previous statutes on the same subject . . . .
    Given this underlying assumption, the rule’s application certainly makes the most
    sense when the statutes were enacted by the same legislative body at the same
    time.”). The Project Bioshield Act of 2004 directs the Secretary of HHS to “award
    contracts, enter into cooperative agreements, or carry out such other activities as
    may reasonably be required in order to ensure that the stockpile [of smallpox
    vaccine] includes an amount of vaccine against smallpox as determined by such
    Secretary to be sufficient to meet the health security needs of the United States.”
    Pub. L. No. 108-276, sec. 3(a)(2), § 319F-2(b)(1), 118 Stat. 835, 843 (2004)
    (codified at 42 U.S.C. § 247d-6b(b)(1) (Supp. V 2005)). It further provides that
    “[n]othing in this section shall be construed to limit the private distribution,
    purchase, or sale of vaccines from sources other than the stockpile.” 
    Id. § 247d-
    6b(b)(2). Although the criminal prohibition in section 175c exempts “conduct by,
    or under the authority of, the Secretary of Health and Human Services,” 18 U.S.C.
    9
    This hypothesis finds support in the legislative history of related enactments. See 150 Cong. Rec.
    15,576 (July 14, 2004) (“Terrorists may soon be able to genetically manipulate biological agents so
    they are resistant to our current stockpile of countermeasures . . . . This legislation recognizes the fact
    that the growing power of biotechnology can render a pathogen like anthrax or smallpox immune to the
    vaccines and drugs we may develop . . . .”) (statement of Rep. Turner on Project Bioshield Act of
    2004); 148 Cong. Rec. 8783 (2003) (“my colleagues and I learned that biological weapons engineers in
    the former Soviet Union had conducted chilling experiments to make these already deadly pathogens
    [anthrax, Ebola, and smallpox] yet more lethal through genetic engineering”) (statement of Sen.
    Kennedy on Conference Report on Public Health Security and Bioterrorism Preparedness and
    Response Act of 2004, which imposed sentences of up to five years for unlawful possession of
    smallpox and other biological agents and toxins).
    111
    Opinions of the Office of Legal Counsel in Volume 32
    § 175c(a)(2), interpreting the definition of variola virus in section 175c to include
    vaccinia might subject the private distribution, purchase, or sale of vaccines
    otherwise permitted by the Act to criminal penalties, since vaccinia continues to be
    used in the manufacture of smallpox vaccine. 10 Such criminal liability could extend
    even to doctors who administer smallpox vaccine to their patients. It would make
    no sense for Congress to impose criminal penalties on the possession of the most
    effective smallpox countermeasure, even if vaccinia were determined at some
    future date to have evolved from variola. Like the “covered countermeasure”
    provision cited above, the Project Bioshield Act makes clear that Congress
    considered vaccinia, at least, to have “legitimate private use[s]” despite its close
    genetic relationship to variola. Under the narrower reading of “derivative,”
    however, there is no tension between the two statutes, both of which are aimed at
    combating bioterrorism. Rather, this interpretation produces “a symmetrical and
    coherent regulatory scheme,” and allows us to “fit . . . all parts [of the relevant
    statutes] into an harmonious whole.” FDA v. Brown & Williamson Tobacco Corp.,
    
    529 U.S. 120
    , 133 (2000) (quotation marks and citations omitted); cf. 
    id. at 138–39
    (finding that the “collective premise” of numerous tobacco-related statutes enacted
    by Congress forecloses an interpretation of the FDCA that would allow the FDA
    to ban tobacco). 11
    C.
    After applying the traditional tools of statutory interpretation, we conclude that
    the better reading of section 175c limits “derivative” to viruses made through
    human intervention and therefore does not cover other orthopoxviruses that may
    have evolved naturally from variola at some point in the past. We cannot, howev-
    er, exclude as unreasonable an interpretation of the statute that would also cover
    naturally occurring “derivatives.” Accordingly, there remains some ambiguity
    with respect to the term “derivative.” The rule of lenity, however, counsels in
    favor of resolving this residual ambiguity in favor of the narrower interpretation.
    See, e.g., Castillo v. United States, 
    530 U.S. 120
    , 131 (2000) (using rule of lenity
    as additional support for preferred interpretation); Jones v. United States, 
    529 U.S. 848
    , 858 (2000) (same); Hughey v. United States, 
    495 U.S. 411
    , 422 (1990)
    10
    The House Report on the Project Bioshield Act indicated an intent to encourage and provide
    incentives for private research and development of vaccines, noting that “[c]urrently, companies have
    little incentive to research, develop, or produce vaccines . . . simply for a possible one-time purchase by
    the Federal government for the Strategic National Stockpile. . . . The Project Bioshield Act is designed
    to help resolve these problems.” H.R. Rep. No. 108-147, pt. 3, at 17 (2003).
    11
    In light of our conclusion that section 175c does not apply to other naturally occurring orthopox-
    viruses, since those orthopoxviruses do not fall within the statutory definition of “variola virus,” we
    need not address the scope of section 175c’s exemption for “conduct by, or under the authority of the
    Secretary of Health and Human Services.”
    112
    Scope of the Definition of “Variola Virus” Under the IRTPA of 2004
    (“Even were the statutory language . . . ambiguous, longstanding principles of
    lenity . . . preclude our resolution of the ambiguity against petitioner.”).
    In general, “‘ambiguity concerning the ambit of criminal statutes should be
    resolved in favor of lenity,’ . . . and . . . ‘when choice has to be made between two
    readings of what conduct Congress has made a crime, it is appropriate, before we
    choose the harsher alternative, to require that Congress should have spoken in
    language that is clear and definite.’” 
    Jones, 529 U.S. at 858
    (quoting Rewis v.
    United States, 
    401 U.S. 808
    , 812 (1971); United States v. Universal C.I.T. Credit
    Corp., 
    344 U.S. 218
    , 221–22 (1962)). This canon of construction “ensures that
    criminal statutes will provide fair warning concerning conduct rendered illegal.”
    Liparota v. United States, 
    471 U.S. 419
    , 427 (1985); see also United States v.
    Lanier, 
    520 U.S. 259
    , 266 (1997) (noting that “the canon of strict construction of
    criminal statutes, or rule of lenity, ensures fair warning by so resolving ambiguity
    in a criminal statute as to apply it only to conduct clearly covered”).
    To be sure, resort to the rule of lenity is justified only where, after “seiz[ing]
    everything from which aid can be derived,” we are “still left with an ambiguous
    statute.” Chapman v. United States, 
    500 U.S. 453
    , 463 (1991) (quotation marks
    and citations omitted). Nor is it appropriate to invoke the rule “merely because it
    [is] possible to articulate a construction more narrow” than another. Moskal v.
    United States, 
    498 U.S. 103
    , 108 (1990) (emphasis in original). Instead, the rule of
    lenity is “reserved . . . for those situations in which reasonable doubt persists about
    a statute’s intended scope even after resort to the language and structure, legisla-
    tive history, and motivating policies of the statute.” 
    Id. (quotation marks
    and
    citation omitted, emphasis in original).
    We have thoroughly examined the language and structure of section 175c and
    the enacted statutory purpose of the provision, as well as the interactions between
    section 175c and related statutes. Invocation of the rule of lenity is therefore
    appropriate with respect to the residual ambiguity in the term “derivative” and
    supports choosing the narrower interpretation—something produced by human
    intervention. More specifically, we believe that the better interpretation of the
    statute would not include within the definition of “variola virus” naturally
    occurring animal orthopoxviruses, such as cowpox, vaccinia, and monkeypox,
    even if one or more of these viruses were eventually determined to have evolved
    from variola. In any event, Congress certainly has not made clear its intent to
    cover these viruses. See Dunn v. United States, 
    442 U.S. 100
    , 112–13 (1979) (rule
    of lenity “is rooted in fundamental principles of due process which mandate that
    no individual be forced to speculate, at peril of indictment, whether his conduct is
    prohibited” and “to ensure that a legislature speaks with special clarity when
    marking the boundaries of criminal conduct, courts must decline to impose
    punishment for actions that are not ‘plainly and unmistakably’ proscribed”)
    (quoting United States v. Gradwell, 
    243 U.S. 476
    , 485 (1917)).
    113
    Opinions of the Office of Legal Counsel in Volume 32
    III.
    For the reasons set forth above, we conclude that the phrase “derivative of the
    variola major virus” as used in section 175c of title 18 refers only to viruses
    produced, synthesized, or engineered from variola major virus or its components
    through human manipulation.
    STEVEN G. BRADBURY
    Principal Deputy Assistant Attorney General
    Office of Legal Counsel
    114