 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued April 10, 2017                  Decided July 21, 2017

                        No. 16-1128

        COMPETITIVE ENTERPRISE INSTITUTE, ET AL.,
                     PETITIONERS

                              v.

  UNITED STATES DEPARTMENT OF TRANSPORTATION AND
 ELAINE L. CHAO, IN HER OFFICIAL CAPACITY AS SECRETARY
      OF THE U.S. DEPARTMENT OF TRANSPORTATION,
                      RESPONDENTS


          On Petition for Review of a Final Rule of
       the United States Department of Transportation


     Sam Kazman argued the cause for petitioners. With him on
the briefs was Hans Bader.

     Tara S. Morrissey, Attorney, U.S. Department of Justice,
argued the cause for respondents. With her on the brief were
Benjamin C. Mizer, Principal Deputy Assistant Attorney
General at the time the brief was filed, Matthew M. Collette,
Attorney, Paul M. Geier, Assistant General Counsel for
Litigation and Enforcement, U.S. Department of Transportation,
Robert M. Gorman, Trial Attorney, Paula Lee, Trial Attorney,
and Blane A. Workie, Assistant General Counsel for Aviation
Enforcement and Proceeding.
                               2

   Before: KAVANAUGH, Circuit Judge, and GINSBURG and
RANDOLPH, Senior Circuit Judges.

   Opinion for the Court filed by Senior Circuit Judge
RANDOLPH.

    Concurring opinion filed by Circuit Judge KAVANAUGH.

    Dissenting opinion filed by Senior Circuit Judge
GINSBURG.

     RANDOLPH, Senior Circuit Judge: The principal question
is whether a statutory ban on “smoking” on airplanes may
support a Department of Transportation regulation banning the
use of electronic cigarettes. Two organizations and an e-
cigarette user ask us to set aside the regulation on the ground
that it is unlawful.

                               I.

     Since 1973, federal law has regulated smoking on airplanes.
Early regulations rested on a statute requiring “safe and
adequate” in-flight service. See 38 Fed. Reg. 12,207, 12,208
(1973) (relying on Federal Aviation Act, Pub. L. No. 85-726,
§ 404(a), 72 Stat. 731, 760 (1958), amended by Pub. L. No. 92-
259 (1972)). See also Action on Smoking & Health v. C.A.B.,
699 F.2d 1209, 1211 (D.C. Cir. 1983). In 1987, Congress
declared it unlawful “to smoke” on scheduled passenger flights
under two hours, and since 2000, the statutory smoking
prohibition has extended to all scheduled passenger flights for
travel within, to, and from the United States. See Pub. L. No.
100-202, § 328, 101 Stat. 1329, 1329-382 (1987); Pub. L. No.
106-181, § 708, 114 Stat. 61, 159 (2000) (codified at 49 U.S.C.
§ 41706). Department of Transportation regulations prohibit the
same. 14 C.F.R. §§ 252.1-252.5.
                                3

     In 2010, during a Senate committee hearing, the
Transportation Department claimed that the statutory smoking
prohibition applied to a new device: e-cigarettes. Although
analogues to the e-cigarette have existed for decades, most
observers date the modern e-cigarette to 2003. The Department
stated in the hearing that existing law “already banned” these
increasingly popular devices on passenger airlines and that it
planned to formalize its interpretation in a rulemaking. The
Financial State of the Airline Industry and the Implications of
Consolidation: Hearing Before the S. Comm. on Commerce,
Sci., & Transp., 111th Cong. 80 (2010).

     The Department issued a notice in 2011 proposing a
regulation defining “smoking” on airplanes to include e-
cigarette use. See Smoking of Electronic Cigarettes on Aircraft,
76 Fed. Reg. 57,008, 57,009 (2011). The notice described e-
cigarettes as consisting of three parts: “The replaceable
cartridge, which most often contains liquid nicotine but may
contain other chemicals, the atomizer or heating element, and
the battery and electronics.” Id. When the user inhales through
the mouthpiece, “the electronics detect the air flow and activate
the atomizer, the liquid nicotine is vaporized, and the user
inhales the vapor.” Id. at 57,010 (citation omitted). Although
the Department noted that e-cigarettes heat rather than burn the
liquid nicotine solution and produce a “vapor, rather than
smoke,” it claimed that e-cigarettes involve an “inhalation and
exhalation similar to smoking cigarettes.” Id. at 57,009-10. The
liquid nicotine solution is partly derived from tobacco plants and
some evidence suggested that the exhaled nicotine vapor could
harm non-users. Id. The Department therefore saw “no reason
to treat electronic cigarettes any differently than traditional
cigarettes.” Id. at 57,009.

    The Department rested its authority for the regulation on the
two sections authorizing past aircraft smoking regulations. Id.
                                 4

The first prohibits “smoking” on scheduled passenger flights
within, to, or from the United States. 49 U.S.C. § 41706. The
second is the current iteration of the “safe and adequate” statute:
it states that an “air carrier shall provide safe and adequate
interstate air transportation.” 49 U.S.C. § 41702. The
Department invited comments on its statutory authority and the
soundness of the rule. 76 Fed. Reg. at 57,009, 57,010.

     After receiving more than 1000 comments, the Department
issued its final rule defining e-cigarette use as “smoking.”1 The
Department focused on the similarity between conventional
cigarettes and e-cigarettes. “Like traditional smoking, e-
cigarette use introduces a cloud of chemicals into the air that
may be harmful to passengers who are confined in a narrow area
within the aircraft cabin without the ability to avoid those
chemicals.” Use of Electronic Cigarettes on Aircraft, 81 Fed.
Reg. 11,415, 11,420 (2016). Several studies “detected toxic
chemicals” from the vapor produced by e-cigarettes. Id. The
Department acknowledged that the “specific hazards” of e-
cigarette vapor have not “yet been fully identified,” but given
the unique setting of air travel, it found a “precautionary
approach” warranted. Id. The Department added that even “if
second-hand exposure to e-cigarette” vapor were ever
determined safe relative to tobacco smoke, “nearby passengers
may still experience discomfort, stress or . . . display aggression
or fear because they believe their health is threatened.” Id. at
11,424. The Department also noted that airlines on their own
already forbid e-cigarette use: “99 percent of passenger
enplanements occur on flights that prohibit smoking of any type,

    1
       The new rule also applies to charter flights when a flight
attendant is required, in accord with a 2012 amendment to § 41706
that prohibits smoking on those flights. See 81 Fed. Reg. 11,415,
11,416, 11,425 (2016); FAA Modernization and Reform Act of 2012,
Pub. L. No. 112-95, § 401(a), 126 Stat. 11, 83 (2012). Petitioners do
not argue against this portion of the rule, so we do not address it.
                                  5

including both traditional cigarettes and e-cigarettes.” Id.
Incorporating these and other considerations into a qualitative
cost-benefit analysis, the Department found the regulation
warranted. Id. at 11,422, 11,425-26. It relied on the two
statutory sources discussed above.2 Id. at 11,419.

     The final rule defines smoking as the “use of a tobacco
product, electronic cigarettes whether or not they are a tobacco
product, or similar products that produce a smoke, mist, vapor,
or aerosol, with the exception of products (other than electronic
cigarettes) which meet the definition of a medical device in
section 201(h) of the Federal Food, Drug and Cosmetic Act,
such as nebulizers.” Id. at 11,427. The rule defines “smoking”
for § 41706 as well as for Transportation Department and
Federal Aviation Administration regulations. See 14 C.F.R.
§ 252.3; 14 C.F.R. § 121.317.

     The Competitive Enterprise Institute, the Consumer
Advocates for Smoke-Free Alternatives Association, and
Gordon Cummings petitioned for judicial review. See 49 U.S.C.
§ 46110(a). Cummings submitted a declaration stating that he
had used e-cigarettes on flights in violation of airline policies,
but that he now no longer does so given the penalties for
violating the regulation. See Decl. of Cummings at 1-2. See
also 49 U.S.C. § 46301 (civil fine); 49 U.S.C. § 46316 (criminal
fine). He has standing to challenge the rule. See, e.g., Energy
Future Coal. v. EPA, 793 F.3d 141, 144 (D.C. Cir. 2015). See
also Americans for Safe Access v. DEA, 706 F.3d 438, 443 (D.C.
Cir. 2013).




     2
     The Department also relied on a third source in the final rule, 49
U.S.C. § 41712, but it no longer does so on appeal.
                                    6

                                   II.

      Although the Department claimed in the rulemaking (and in
its brief) that 49 U.S.C. § 41702 and § 41706 provide alternative
authority for the rule, the sections are not co-extensive. The key
difference is in their geographic scope. Section 41702 requires
that an “air carrier” – defined as a “citizen of the United States
undertaking . . . to provide air transportation,” 49 U.S.C.
§ 40102(a)(2) – “provide safe and adequate interstate air
transportation.” The prohibition “against smoking on passenger
flights” in § 41706, on the other hand, covers both domestic and
foreign air carriers for travel within, to, and from the United
States. Because the regulation purports to extend the e-cigarette
prohibition to this latter category of flights, see 81 Fed. Reg. at
11,419, we must first analyze whether § 41706 provides
authority for the rule.

     We begin with Chevron U.S.A. Inc. v. NRDC, 467 U.S. 837
(1984).3 We first ask whether Congress addressed the question
at issue: does “smoking” in § 41706 cover e-cigarette use? See
Nat’l Mining Ass’n v. Kempthorne, 512 F.3d 702, 708-09 (D.C.
Cir. 2008) (citing Chevron, 467 U.S. at 842-43). If Congress did




     3
       Chevron arose under the Clean Air Act, but courts – including
the Supreme Court and our court – have applied the doctrine when
interpreting other statutes. At least as a matter of first principles, this
seems problematic. The Clean Air Act provides its own procedures
and standards for judicial review that differ from other statutes, such
as the Administrative Procedure Act’s instruction to the “reviewing
court” to “interpret constitutional and statutory provisions.” Compare
42 U.S.C. § 7607(d)(9) & (e), with 5 U.S.C. § 706. See also Stephen
G. Breyer, Richard B. Stewart, Cass R. Sunstein & Adrian Vermeule,
ADMINISTRATIVE LAW AND REGULATORY POLICY 250 (6th ed. 2006).
                                  7

not address the question, we next consider whether the
Department’s interpretation is reasonable. Id.44

      Underlying petitioners’ arguments and those of the dissent
is the point that e-cigarettes did not exist in 1987 when Congress
first made it unlawful “to smoke” on certain flights under two
hours, nor did e-cigarettes exist in 2000 when Congress
extended the prohibition. Although this means the legislators
did not have e-cigarettes in mind when passing those statutes,
that does not resolve the interpretive question.51 The text itself,
rather than the subjective intentions of legislators, governs our
review. See Oncale v. Sundowner Offshore Servs., Inc., 523
U.S. 75, 79 (1998). We must ask whether the term “smoking”
in a statute enacted before modern e-cigarettes existed covers
these devices.

     Petitioners maintain that “smoking” in § 41706 requires
lighting or burning and does not encompass the heating that
occurs with e-cigarettes. The statutory text alone offers no
support for that position. Section 41706 employs the verb
“smoke” in various formulations. Subsection (a) states that an
“individual may not smoke” on certain domestic flights.

     4
      We apply the Chevron framework to this facial challenge even
though violating § 41706 can bring criminal penalties. See Babbitt v.
Sweet Home Chapter of Communities for a Great Oregon, 515 U.S.
687, 704 n.18 (1995); In re Sealed Case, 223 F.3d 775, 779 (D.C. Cir.
2000).

     5
       See Antonin Scalia & Bryan A. Garner, READING LAW: THE
INTERPRETATION OF LEGAL TEXTS 86 (2012), quoting Lon L. Fuller,
American Legal Realism, 82 U. PA. L. REV. 429, 445-46 (1934):
“Suppose a legislator enacts that it shall be a crime for anyone ‘to
carry concealed on his person any dangerous weapon.’ After the
statute is passed someone invents a machine, no larger than a fountain
pen, capable of throwing a ‘death ray’. Is such a machine included?
Obviously, yes.”
                                 8

Subsection (b) states that the “Secretary of Transportation shall
require all air carriers and foreign air carriers to prohibit
smoking” on certain foreign flights. Nowhere in § 41706 or
Title 49 is “smoke” or “smoking” defined. The final subsection
of § 41706 states: “The Secretary shall prescribe such
regulations as are necessary to carry out this section.” 49 U.S.C.
§ 41706(d). Whether the regulation before us constitutes a
permissible application of the Department’s rulemaking
authority is thus unclear from the text alone.

       Given the few textual clues in § 41706 itself, both parties
turn to external sources. What do the dictionaries say?
Petitioners cite definitions of “smoking” that require burning.
They invoke Merriam-Webster’s Collegiate Dictionary 1109
(10th ed., 1993 and 1995), for instance, for the proposition that
to smoke means “to inhale and exhale the fumes of burning
plant material and esp. tobacco.” Other dictionary definitions
support the Department. One definition in the Oxford English
Dictionary, for example, defines smoking as to “inhale (and
expel again) the fumes of tobacco, or other suitable substance,
from a pipe, cigar, or cigarette.” 15 OXFORD ENGLISH
DICTIONARY 802 (2d ed. 1989). (Definitions of “fume” often
refer to vapor and do not require fire. See, e.g., 6 OXFORD
ENGLISH DICTIONARY 258-259 (2d ed. 1989).) Webster’s Third
New International Dictionary 2152 (1981), similarly defines
smoking as to “inhale and exhale the fumes of tobacco or
something resembling tobacco from a pipe, cigar, or cigarette.”
These definitions are not only contemporaneous with the
original 1987 statutory smoking prohibition, but they also
describe e-cigarette use: one typically inhales and exhales
vaporized nicotine, derived from tobacco plants, from a battery-
powered “cigarette.” The rulemaking definition – “the use of
. . . electronic cigarettes . . . or similar products that produce a
smoke, mist, vapor, or aerosol . . .,” 81 Fed. Reg. at 11,417 –
echoes these dictionary definitions.
                                9

     Petitioners respond that the Department’s dictionary
definitions are outliers. More dictionary definitions support
their position, they argue, and the mere existence of contrary
definitions does not render the statute ambiguous. See Petitioner
Reply Br. 6 (citing MCI Telecomms. Corp. v. AT&T, 512 U.S.
218, 225-27 (1994)). That all seems true. Establishing
ambiguity is not so simple; but neither is establishing plain
meaning. We cannot just tally the dictionary definitions.

     Petitioners also argue that the “smoking” prohibition cannot
cover e-cigarettes because e-cigarettes do not produce “smoke.”
In the notice of proposed rulemaking, the Department did state
that e-cigarettes produce “a vapor, rather than smoke,” but the
Department referred to e-cigarette vapor as “second hand
smoke.” 76 Fed. Reg. at 57,009, 57,010. The title of the notice
was also “Smoking of Electronic Cigarettes on Aircraft.”
Department characterizations aside, whether e-cigarettes
produce “smoke” is subject to the same conflicting definitions
as the verb form of “smoke” discussed above. Compare
WEBSTER’S THIRD NEW INTERNATIONAL DICTIONARY 2152
(1981) (“the gaseous products of burning carbonaceous
materials made visible by the presence of small particles of
carbon”), with id. (“a fume or vapor often resulting from the
action of heat on moisture”). See also U.S. Fid. & Guar. Co. v.
First State Bank & Trust Co., 125 F.3d 680, 684 (8th Cir. 1997)
(noting conflicting judicial interpretations of noun “smoke”).
Even if e-cigarettes do not produce smoke, the verb “smoking”
can refer to processes where no smoke is produced. The
dictionary definitions of smoking suggest as much, see supra 8,
as do characterizations by the e-cigarette industry itself. One e-
cigarette distributor, for example, has marketed its product for
“smoking pleasure.” See Sottera, Inc. v. FDA, 627 F.3d 891,
893 (D.C. Cir. 2010) (internal quotation marks omitted).

   Both the Department and petitioners also cite definitions of
smoking from sources in the states. Petitioners refer to an
                                10

opinion from the Virginia Attorney General, among other
attorneys general, concluding that smoking does not include e-
cigarette use. See Va. Op. Att’y Gen. No. 10-029 (Apr. 27,
2010). Yet the Department cites many state laws indicating the
opposite. See CAL. BUS. & PROF. CODE § 22950.5(c); DEL.
CODE ANN. tit. 16 § 2902(12); HAW. REV. STAT. § 328J-1; N.J.
STAT. ANN. § 26:3D-57. These state laws resulted from
amendments including e-cigarettes in their prohibitions against
smoking, but that does not mean their definitions without the
amendment, as petitioners claim, would have excluded e-
cigarettes. The states plausibly did what the Department
purported to do: formalize its interpretation that smoking
covered e-cigarette use.

     In their reply brief, petitioners highlight Congress’s failure
to enact proposed bills prohibiting e-cigarette use on airplanes.
See H.R. 636, 114th Cong. § 5030 (as passed by Senate, Apr. 19,
2016); H.R. 3840, 114th Cong. § 2 (2015). See also H.R. 2962,
115th Cong. § 2 (2017). But “Congressional inaction lacks
persuasive significance because several equally tenable
inferences may be drawn from such inaction, including the
inference that the existing legislation already incorporated the
offered change.” Consumer Elecs. Ass’n v. FCC, 347 F.3d 291,
299 n.4 (D.C. Cir. 2003) (quoting Pension Benefit Guaranty
Corp. v. LTV Corp., 496 U.S. 633, 650 (1990)).

      So here is where we are. Although the statute does not
define “smoke,” some dictionary definitions, some state laws,
and some characterizations of smoking by the e-cigarette
industry itself support the Department. But other dictionary
definitions and other state laws support petitioners. We
therefore cannot say that Congress spoke to the precise question
at issue.

     Petitioners present no arguments under Chevron’s second
step “beyond those already discussed as part of step one.” See
                                11

Consumer Elecs. Ass’n, 347 F.3d at 299. The Chevron-one
analysis supports a reasonableness finding. So does our 2010
decision concluding that the Food and Drug Administration can
regulate e-cigarettes as “tobacco products” because the liquid
nicotine solution in e-cigarettes is derived from tobacco plants.
See Sottera, 627 F.3d at 898-99. A “smoking prohibition”
reasonably applies to products intended to enable users to inhale
and exhale such nicotine.

                                III.

     Petitioners also argue that the regulation is arbitrary.61 The
thrust of their argument is that e-cigarette use does not harm
non-users. They cite studies supposedly demonstrating this and
they emphasize that even by the Department’s own
characterization, e-cigarettes present only the potential of harm
to non-users. The Department cites no instance, petitioners add,
of a passenger harmed by in-flight e-cigarette use.

     The Department acknowledges the limited evidence on the
health effects of e-cigarettes but claims that a “precautionary
approach” is warranted. 81 Fed. Reg. at 11,420. At first blush,
this approach – based apparently on the “precautionary
principle” – may appear convincing. Some studies suggest that
e-cigarette vapor may harm non-users. The agency therefore
acts sensibly, the thinking goes, when it prevents this possible
harm by prohibiting e-cigarette use.

    This approach to regulation has been criticized. The
precautionary principle “imposes a burden of proof on those
who create potential risks, and it requires regulation of activities
even if it cannot be shown that those activities are likely to

    6
      Although petitioners formally tie their arbitrariness and
procedural arguments to the “safe and adequate” provision, 49 U.S.C.
§ 41702, we shall address the arguments that apply to § 41706.
                                12

produce significant harms. Taken in this strong form, the
precautionary principle should be rejected, not because it leads
in bad directions, but because it leads in no direction at all. The
principle is literally paralyzing – forbidding inaction, stringent
regulation, and everything in between. The reason is that in the
relevant cases, every step, including inaction, creates a risk to
health, the environment, or both.” Cass R. Sunstein, Beyond the
Precautionary Principle, 151 U. PA. L. REV. 1003, 1003 (2003).

     But in this case the Department did more than simply
invoke a “precautionary approach.” It determined that the
benefits of the regulation justify the costs. One factor reduced
both sides of the ledger: airlines already prohibit e-cigarette use
on flights. 81 Fed. Reg. at 11,423. Given that backdrop, the
costs and benefits primarily flow from those users, like
petitioner Cummings, who would otherwise defy the airlines’
prohibitions and take the chance of using e-cigarettes on flights,
but will now refrain from doing so given the regulation.

     As the Department pointed out, the costs are modest. The
small subset of passengers like Cummings is inconvenienced,
but those passengers can still use other nicotine products on
flights. Id. at 11,426. The availability of these “alternative
nicotine delivery systems” coupled with the “lack of flight
alternatives,” the Department concluded, also means that the
regulation will have a minimal effect on the number of
passengers flying. Id. Any “reduction in demand from
smokers” may also “be offset by increased demand from non-
smokers.” Id. Costs of the regulation would increase if the
airlines wanted to allow e-cigarette use on flights, but so would
the benefits.

    The benefits of the regulation are also modest, but the
Department reasonably concluded that they justify the costs.
The Department identified three benefits in particular. The first
                             13

concerns the health of non-users. The Department found that e-
cigarette users would now no longer introduce a “cloud of
chemicals into the air that may be harmful to passengers.” Id.
at 11,420, 11,425. The Department cited seven studies
discussing this potential harm. Id. at 11,420. Some
representative conclusions from the studies:

    • “Our data confirm that e-cigarettes are not emission-free
      and their pollutants could be of health concern for users
      and secondhand smokers,” Wolfgang Schober et al.,
      Use of Electronic Cigarettes (E-cigarettes) Impairs
      Indoor Air Quality and Increases FeNO Levels of E-
      Cigarette Consumers, 217 INT’L J. HYGIENE & ENVTL.
      HEALTH 628, 628 (2014);

    • “The vapour generated from e-cigarettes contains
      potentially toxic compounds,” Maciej Goniewicz et al.,
      Levels of Selected Carcinogens and Toxicants in Vapour
      from Electronic Cigarettes, 23 TOBACCO CONTROL 133,
      138 (2014);

    • “The study showed that e-cigarettes are a source of
      secondhand exposure to nicotine but not to combustion
      toxicants,” Jan Czogala et al., Secondhand Exposure to
      Vapors from Electronic Cigarettes, 16 NICOTINE &
      TOBACCO RES. 655, 655 (2014);

    • “Cartomizer aerosol from a leading manufacturer of [e-
      cigarettes] contained metals, silicate beads, and
      nanoparticles,” Monique Williams et al., Metal and
      Silicate Particles Including Nanoparticles Are Present
      in Electronic Cigarette Cartomizer Fluid and Aerosol,
      PloS ONE, Mar. 2013, at 1, 5.
                                14

     These studies may have flaws, but they tend to show that e-
cigarette vapor in confined aircrafts could harm non-users.
Especially due to the “involuntary nature” of secondhand
exposure on aircrafts, where individuals are often assigned seats,
the Department gave particular weight to these health risks. 81
Fed. Reg. at 11,426. “Those seated next to users may not want
to expose themselves (or their babies or older children)” to even
small risks, the Department concluded. Id.

     Petitioners criticize these studies, but even a study
petitioners rely on cautions that “electronic cigarettes cannot be
considered safe.” See Zachary Cahn & Michael Siegel,
Electronic Cigarettes as a Harm Reduction Strategy for
Tobacco Control: A Step Forward or a Repeat of Past
Mistakes?, 32 J. PUB. HEALTH POL’Y 16, 26 (2011). Petitioners
also acknowledge that “the studies cited by the agency” “show
that e-cigarette vapor might introduce into indoor air certain
chemicals, some of which, if present in high concentrations,
might pose a health risk.” Petitioner Br. 34. The Department
sought to reduce this health risk with the regulation.

     The regulation’s two other benefits do not depend on the
health effects of e-cigarettes. Specifically, the Department noted
that prohibiting e-cigarette use would avoid passenger
perception of harm – itself a harm. In short, some passengers
are not comfortable inhaling the visible mist produced by e-
cigarettes. Passengers “may reasonably be concerned,” the
Department explained, “that they are inhaling unknown
quantities of harmful chemicals.” 81 Fed. Reg. at 11,421.
Commenters on the rule expressed these concerns, and this fear
alone could cause “discomfort” and “stress” for passengers.
See, e.g., Comment of E. Schiller, ID: DOT-OST-2011-0044-
0124; 81 Fed. Reg. at 11,424. The Department also concluded
that the rule will make it easier for airlines to enforce their own
e-cigarette prohibitions. 81 Fed. Reg. at 11,425. Partly for this
                                  15

reason, associations of flight attendants and pilots supported the
rule. See id. at 11,417.

     Concluding that these benefits justify the costs reflects a
“rational connection between the facts found and the choice
made.” Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm
Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983) (internal quotation
marks omitted). The regulation is thus not arbitrary.7

                                  IV.

    Petitioners also raise two procedural objections. They first
argue that the Department failed to respond to the contrary
studies that they submitted during the comment period. Yet the
Department acknowledged the petitioners’ contrary evidence
and explained why the regulation was still warranted. See 81
Fed. Reg. at 11,418, 11,419-21. The Department noted the other
scientific studies and non-scientific justifications for the rule.
Id.

    Petitioners’ second procedural argument concerns the
studies cited in the final rule. Specifically, they argue that the
Department impermissibly relied on new studies in the final rule
without providing the public an opportunity to comment on
     7
       Petitioners also argue that the risks from e-cigarettes do not
exceed the risks from other substances and contaminants found on
airplanes. But the relevant statute instructs the Department to regulate
“smoking,” 49 U.S.C. § 41706, not these other substances. In any
case, the “agency enjoys broad discretion in determining how best to
handle related, yet discrete, issues in terms of procedures and
priorities.” Mobil Oil Exploration & Producing Se., Inc. v. United
Distribution Cos., 498 U.S. 211, 230 (1991) (citations omitted). It
need not “make progress on every front before it can make progress
on any front.” Pers. Watercraft Indus. Ass’n v. Dep’t of Commerce,
48 F.3d 540, 544 (D.C. Cir. 1995) (quoting United States v. Edge
Broadcasting Co., 509 U.S. 418, 434 (1993)).
                                 16

them. An agency cannot include material “critical” to its
decision for the first time in the final rule, Pers. Watercraft
Indus. Ass’n v. Dep’t of Commerce, 48 F.3d 540, 544 (D.C. Cir.
1995), but it may include new “supplementary” information that
“expands on and confirms” data in the rulemaking record.8
Solite Corp. v. U.S. EPA, 952 F.2d 473, 484 (D.C. Cir. 1991)
(per curiam) (alterations omitted) (quoting Community Nutrition
Institute v. Block, 749 F.2d 50, 58 (D.C. Cir. 1984)). This case
falls in the latter category. In the notice of proposed
rulemaking, the Department cited two studies and three articles
describing the potential harm from e-cigarettes, and it cited
seven different, more recent studies describing the same in the
final rule. See 76 Fed. Reg. at 57,010; 81 Fed. Reg. at 11,420.
Those new studies did not provide critical new data, but instead
“continue[d] to undermine claims that the use of e-cigarettes
would have no adverse health implications on users or others
who are nearby” and thus further supported the Department’s
reasoning in the notice of proposed rulemaking. 81 Fed. Reg. at
11,420.

     In their reply brief, petitioners argue that an agency cannot
even cite supplementary data in its final rule if the new data
prejudices them. That is incorrect. Petitioners support their
proposed standard with dicta from past cases blurring the rule
itself with the Administrative Procedure Act’s harmless error
rule. See generally Ozark Auto. Distributors, Inc. v. NLRB, 779
F.3d 576, 582-83 (D.C. Cir. 2015) (discussing harmless error

    8
       This proposition derives from 5 U.S.C. § 553. See Owner-
Operator Indep. Drivers Ass’n, Inc. v. Fed. Motor Carrier Safety
Admin., 494 F.3d 188, 199 (D.C. Cir. 2007). On the apparent
disconnect between the text of § 553 and the requirements concerning
“critical” new data, see Am. Radio Relay League, Inc. v. FCC, 524
F.3d 227, 246-247 (D.C. Cir. 2008) (Kavanaugh, J., concurring in part
and dissenting in part); 1 Richard J. Pierce, ADMINISTRATIVE LAW
TREATISE § 7.3, at 583-84, 591 (5th ed. 2010).
                                17

rule in 5 U.S.C. § 706). We have written, for instance, that “an
agency may use supplementary data . . . so long as no prejudice
is shown.” See, e.g., Chamber of Commerce of U.S. v. SEC, 443
F.3d 890, 900 (D.C. Cir. 2006) (emphasis added) (internal
quotation marks omitted). Other statements and our actual
rulings, however, treat both a violation of the rule and a showing
of prejudice as necessary conditions for vacatur. See, e.g., id. at
904; Am. Radio Relay League, Inc. v. FCC, 524 F.3d 227, 236-
37 (D.C. Cir. 2008); Owner-Operator Indep. Drivers Ass’n, Inc.
v. Fed. Motor Carrier Safety Admin., 494 F.3d 188, 202 (D.C.
Cir. 2007). Still other cases do not even refer to the prejudice
inquiry after finding no violation of the rule. See Int’l Fabricare
Inst. v. U.S. EPA, 972 F.2d 384, 399-400 (D.C. Cir. 1992) (per
curiam). No case, to our knowledge, has ever vacated a
regulation after finding prejudice but no violation of the notice
requirement. That is no surprise: we need not assess whether an
error prejudices the petitioner if the agency did not err.

    We therefore reject petitioners’ procedural arguments.

                                V.

     For the reasons stated above, we deny the petition for
review. Because we uphold the regulation under 49 U.S.C.
§ 41706, we need not address § 41702.

                                                     So ordered.
     KAVANAUGH, Circuit Judge, concurring: I join the
majority opinion and add these brief comments. Even without
affording Chevron deference to the Department’s
interpretation of the statute, I would still reach the same result
in this case. In my view, although it is a close call, the better
interpretation of the term “smoking” in this statute covers e-
cigarettes as well as conventional tobacco cigarettes. Judge
Ginsburg’s fine dissent rests in part on the notion that those
who drafted or read the statute in 1987 would not have
understood the term “smoking” to encompass e-cigarettes
because e-cigarettes did not exist at that time. I am not
convinced by that line of analysis, for reasons that the majority
opinion persuasively explains. See Maj. Op. at 7 & n.5.
      GINSBURG, Senior Circuit Judge, dissenting: An axiom
of statutory interpretation is that “unless otherwise defined,
words will be interpreted as taking their ordinary,
contemporary, common meaning . . . at the time Congress
enacted the statute.” Perrin v. United States, 444 U.S. 37, 42
(1979). Today this Court departs from this principle to
redefine “smoking” from conventional tobacco consumption,
as it was commonly understood in 1987, to prohibit the use of
electronic cigarettes, a new technology with a substantially
different nicotine delivery process and likely different
secondhand effects as well. Just as some people will, no
doubt, “find ambiguity even in a ‘No Smoking’ sign,” Int’l
Union v. Gen. Dynamics Land Sys. Div., 815 F.2d 1570, 1575
(D.C. Cir. 1987), the Court manufactures ambiguity from the
lack of a statutory definition and some abstract dictionary
definitions of “smoking” even though the Congress that
adopted the statute and the public it represented would have
found the term unambiguous when relating to passenger
aviation.

     Just as historical understandings define the meaning of
statutory terms, whether terms are ambiguous is determined
as of the time when the Congress passed the law. See Terrell
v. United States, 564 F.3d 442, 449 (6th Cir. 2009).
Subsequent changes in society, technology, or the English
language do not alter the meaning of a statute. For example,
the Supreme Court held in 2004 that sand and gravel in
Nevada were not “valuable” minerals under the Pittman Act
of 1919 even though development of the region in the
intervening 85 years had made those commodities
commercially exploitable. BedRoc Ltd., LLC v. United States,
541 U.S. 176, 183-85 (plurality opinion); id. at 187-89
(Thomas, J. concurring) (reaching same conclusion as the
plurality because sand and gravel in Nevada lacked a
“commercial purpose” at the time of enactment). Likewise,
the Court has said gaseous methane was not “coal”
“reserv[ed] to the United States” in government land grants,
                               2
even though advances in scientific knowledge later
determined the gas was a commercially valuable part of the
coal itself. Amoco Prod. Co. v. S. Ute Indian Tribe, 526 U.S.
865, 870, 872-75 (1999). Following the Supreme Court’s
lead, the courts of appeals have similarly refused to depart
from the original meaning of statutory terms notwithstanding
subsequent changes in technology and the law. See Terrell,
564 F.3d at 451-52 (reading “appear” to require an in-person
appearance at a parole hearing because videoconferencing
was not technologically feasible at the time of enactment);
Texas v. United States, 497 F.3d 491, 503-04 (5th Cir. 2007)
(rejecting the proposition that “a judicial decision can, ex post
facto, create a Chevron-type ‘gap’ that introduces ambiguity
into the operation of a statutory scheme”). United States v.
Brune, 767 F.3d 1009, 1022 (10th Cir. 2014) (holding a
statute does not criminalize Internet access because the
medium would not have been considered “any other material
that contains an image of child pornography” at the time of
enactment in 1996); McDonald v. Sun Oil Co., 548 F.3d 774,
779-81 (9th Cir. 2008) (holding the Comprehensive
Environmental Response, Compensation, and Liability Act
preempts both “statutes of repose” and, as stated in the text,
“statutes of limitations” because those terms were used
interchangeably when enacted in 1986 even though they are
now considered “distinct legal concepts”), abrogated by CTS
Corp. v. Waldburger, 134 S. Ct. 2175, 2185-87 (2014)
(analyzing those terms as they were understood in 1986 but
reaching a different conclusion for other reasons).

     The Court resists the historical meaning of “smoking” in
two ways. First, it holds the term “smoking” was always
understood more broadly than conventional tobacco
combustion. As evidence, the Court points to dictionary
definitions of “smoke” and “smoking” from the 1980s, which
it construes to cover e-cigarette usage. True, e-cigarettes
                              3
might fit within these definitions if one squints hard enough,
but as the Court itself notes “[w]e cannot just tally the
dictionary definitions,” Ct. Op. 9, because “[a]mbiguity is a
creature not of definitional possibilities but of statutory
context,” Brown v. Gardner, 513 U.S. 115, 118 (1994). See
also U.S. Fid. & Guar. Co. v. First State Bank & Trust Co.,
125 F.3d 680, 684 (8th Cir. 1997) (cited by Ct. Op. 9)
(disagreeing with “appellants’ definition of the term ‘smoke’
because a term’s ordinary meaning is derived from the
interpretation of lay persons rather than the definition
provided in a dictionary”). That context – a ban on “smoking”
on passenger flights – overwhelmingly confirms the narrow
scope of the prohibition in § 41706.

     What “smoking” meant in 1987 with respect to
passengers on airplanes is beyond doubt, inasmuch as e-
cigarettes did not then exist. But like the Court, one could
stretch dictionary definitions to apply to a wide range of
activities no one would have understood the ban to cover at
the time. For example, if one defines “smoke” as “the action
of heat on moisture,” Ct. Op. 9 (quoting WEBSTER’ S THIRD
NEW INTERNATIONAL DICTIONARY 2152 (1981)), and
“smoking” as “to emit . . . smoke,” ENCYCLOPEDIA
BRITANNICA (1988), then the steam (“to emit . . . smoke”)
from hot coffee (“the action of heat on moisture”), which was
served on airplanes in the 1980s, could also fall within the
ban. Likewise a breath-freshening spray (to “inhale (and expel
again) the fumes,” Ct. Op. 8 (quoting 15 OXFORD ENGLISH
DICTIONARY 802 (2d ed. 1989)), of “[a] suspension of solid or
liquid particles in a gas,” WEBSTER’ S THIRD 2152 (1981)
(quoted by the Department)), could be similarly prohibited.
Each interpretation would have been just as absurd in the
1980s as it is today, yet each follows from a creative use of
dictionary definitions. Although prohibiting a wholly new
product, e-cigarettes, may make more sense to modern
                               4
passengers, the sentiment of today says nothing about whether
the activity was “smoking” in the 1980s, when e-cigarettes
did not exist.

     The Court’s second theory about the broad meaning of
“smoking” suffers from a similarly anachronistic mindset. To
wit, the Court cites industry characterizations of e-cigarettes
as being for one’s “smoking pleasure.” Ct. Op. 9-10 (quoting
Sottera, Inc. v. FDA, 627 F.3d 891, 893 (D.C. Cir. 2010)
(stating in dicta that e-cigarette liquids are “tobacco products”
“derived from tobacco” and regulated under the Tobacco Act
but not deciding whether their use is “smoking”)). It also
points to several states that have recently extended statutory
bans on “smoking” to prohibit e-cigarettes in addition to
conventional tobacco. On the first point, contemporary
industry marketing efforts alone cannot determine the
meaning of a statutory term adopted 30 years ago. Were that
the case, an industry could opportunistically characterize its
products to fall either inside or outside of a regulatory
scheme, undermining the purpose of the statute.

     On the second point, the Court is correct that some states
have amended their statutory bans to cover e-cigarettes. 1 But
in each state cited, the legislature, not an executive agency,
amended the statutory prohibition, exercising legislative
power it undoubtedly possessed. If the Congress had taken the
same action, which it has considered but not done, Ct. Op. 10
(citing H.R. 636, 114th Cong. § 5030 (as passed by the
Senate, Apr. 19, 2016); H.R. 3840, 114th Cong. § 2 (2015)),
then there would be no serious question of the Department’s

       1
          Other states, however, have not. See Va. Op. Att’y Gen.
Op. No. 10-029 (Apr. 27, 2010); Ariz. Att’y Gen. Op. No. I14-004
(R14-012), (July 30, 2014); Kan. Att’y Gen. Op. No. 2011-015
(Oct. 31, 2011).
                                  5
authority, but absent legislative action or an alternative source
of regulatory authority, 2 I cannot accept the Court’s
ahistorical reinterpretation of a purportedly ambiguous
statutory term that was well-understood when enacted in
1987.

     I respectfully dissent.




        2
          The Department also argued the Rule can be upheld under
its authority to require “safe and adequate” service in passenger
aviation. See 49 U.S.C. § 41702. As the Court correctly notes, this
authority extends only to domestic air carriers, unlike the statutory
ban on “smoking,” which also applies to international flights.
Because the Court affirmed the ban on the latter, broader ground, I
have no cause to address whether it could have been justified on the
narrower “safe and adequate” theory. For this reason, I do not
address Parts III through V of the Court’s opinion on procedural
irregularities in the rulemaking, which are relevant only to the “safe
and adequate” rationale.
