                 FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT


COMMITTEE FOR A BETTER ARVIN, a          No. 11-73924
California nonprofit corporation;
COMITE RESIDENTES ORGANIZADOS
AL SERVICIO DEL AMBIENTE SANO,
an unincorporated association;
ASSOCIATION OF IRRITATED
RESIDENTS, an unincorporated
association,
                          Petitioners,

                  v.

U.S. ENVIRONMENTAL PROTECTION
AGENCY; LISA P. JACKSON,
Administrator, U.S. Environmental
Protection Agency; JARED
BLUMENFELD, Regional
Administrator, Region IX, U.S.
Environmental Protection Agency,
                       Respondents,

SAN JOAQUIN VALLEY UNIFIED AIR
POLLUTION CONTROL DISTRICT,
           Respondent-Intervenor.
2         COMM. FOR A BETTER ARVIN V. EPA

COMMITTEE FOR A BETTER ARVIN, a          No. 12-71332
California nonprofit corporation;
COMITE RESIDENTES ORGANIZADOS
AL SERVICIO DEL AMBIENTE SANO,
an unincorporated association;            OPINION
ASSOCIATION OF IRRITATED
RESIDENTS, an unincorporated
association,
                          Petitioners,

                  v.

U.S. ENVIRONMENTAL PROTECTION
AGENCY; GINA MCCARTHY,
Administrator, U.S. Environmental
Protection Agency; JARED
BLUMENFELD, Regional
Administrator, Region IX, U.S.
Environmental Protection Agency,
                       Respondents,

SAN JOAQUIN VALLEY UNIFIED AIR
POLLUTION CONTROL DISTRICT,
           Respondent-Intervenor.


       On Petition for Review of an Order of the
     United States Environmental Protection Agency

                Argued and Submitted
        October 22, 2014—Pasadena, California

                   Filed May 20, 2015
             COMM. FOR A BETTER ARVIN V. EPA                          3

Before: Sidney R. Thomas, Chief Judge, and Alex Kozinski
           and Ronald M. Gould, Circuit Judges.

                     Opinion by Judge Gould


                           SUMMARY*


                       Environmental Law

    The panel granted in part, and denied in part, a petition
for review brought by several environmental and community
organizations challenging the Environmental Protection
Agency’s approval of California’s State Implementation
Plans to comply with National Ambient Air Quality
Standards enacted under the federal Clean Air Act,
concerning ozone and fine particulate matter in the San
Joaquin Valley.

    The panel held that the EPA violated the Clean Air Act by
approving California’s plans even though the plans did not
include the state-adopted mobile emissions standards on
which those plans relied to achieve their emission reduction
goals. The panel further held that the EPA did not violate the
Clean Air Act by not requiring inclusion of other state
mechanisms in its plans. The panel also held that other
control measures approved by the EPA were enforceable
commitments as the Clean Air Act required. The panel
remanded to the EPA for further proceedings.


  *
    This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
4          COMM. FOR A BETTER ARVIN V. EPA

                        COUNSEL

Brent Newell (argued), Sofia L. Parino, Center on Race,
Poverty & the Environment, San Francisco, California; Laura
Baker, Center on Race, Poverty & the Environment, Delano,
California, for Petitioners.

Heather E. Gange (argued), Ignacia S. Moreno, Dustin J.
Maghamfar, United States Department of Justice,
Washington, D.C.; Jeanhee Hong, Jefferson Wehling, United
States Environmental Protection Agency, San Francisco,
California; Jan Tierney, Geoffrey L. Wilcox, United States
Environmental Protection Agency, Washington, D.C., for
Respondents.

Annette A. Ballatore-Williamson (argued), Catherine T.
Redmond, San Joaquin Valley Unified Air Pollution Control
District, Fresno, California, for Respondent-Intervenor.


                        OPINION

GOULD, Circuit Judge:

    Petitioners, a contingent of environmental and community
groups, bring serious challenges to the State of California’s
plans to improve air quality in the San Joaquin Valley, an
area with some of the worst air quality in the United States.
We must consider whether these state plans are sufficient in
law, specifically, whether the regulating United States
Environmental Protection Agency (“EPA”) erred in
approving California’s State Implementation Plans (“SIPs”)
to comply with National Ambient Air Quality Standards
(“NAAQS”) enacted under the federal Clean Air Act
            COMM. FOR A BETTER ARVIN V. EPA                   5

(“CAA”) concerning ozone and fine particulate matter in the
San Joaquin Valley. We do this in the context of a
cooperative federalism regime in which the federal agency
sets required air quality standards but the state is a primary
actor in creating plans to achieve them, followed by potential
enforcement at both state and federal levels and by private
citizens.

    Petitioners contend: (1) that the approved plans calculate
the necessary emissions reductions and forecasts in part based
on state-adopted measures that are not themselves
incorporated into the federally enforceable plan, in violation
of the CAA; (2) that other strategies to gain compliance with
the NAAQS proposed by the California Air Resources Board
(“CARB”) and Intervenor San Joaquin Valley Unified Air
Pollution Control District (“the District”) that are in the EPA-
approved plans are unenforceable goals, rather than the
enforceable commitments that the CAA requires; (3) that
EPA unlawfully approved the plan relating to ozone insofar
as that plan lacked enforceable transportation control
measures; and (4) that the D.C. Circuit’s holding in NRDC v.
EPA, 706 F.3d 428 (D.C. Cir. 2013), that EPA relied on the
wrong statutory provision of the CAA in crafting its fine
particulate matter implementation rule, pursuant to which the
fine particulate matter plan at issue was approved, gives
another important reason to grant the petition.

    We hold that by approving California’s plans even though
the plans did not include the state-adopted mobile emissions
standards on which those plans rely to achieve their emissions
reductions goals, EPA violated the CAA. We also hold that
EPA did not violate the CAA by not requiring inclusion of
other state mechanisms in its plans, and that other control
6                 COMM. FOR A BETTER ARVIN V. EPA

measures approved by EPA are enforceable commitments as
the CAA requires.1

                                         I

    States and the federal government must work together to
improve air quality for individuals nationwide. This is so
because the CAA has established a uniquely important system
of cooperative federalism in the quest for clean air. “The
CAA makes the States and the Federal Government partners
in the struggle against air pollution.” Jensen Family Farms,
Inc. v. Monterey Bay Unified Air Pollution Control Dist.,
644 F.3d 934, 938 (9th Cir. 2011) (quoting Gen. Motors
Corp. v. United States, 496 U.S. 530, 532 (1990) (internal
quotation marks omitted)). The CAA protects the nation’s air
quality by authorizing EPA to establish NAAQS that apply to
air pollutants. 42 U.S.C. § 7409.2 EPA designates areas that
fail to attain the NAAQS as “nonattainment areas.” Id.
§ 7407(d)(1).

                                        A

   The CAA requires states to address nonattainment areas
by developing a SIP that lays out a plan for how a
nonattainment area will eventually comply with the NAAQS.
42 U.S.C. §§ 7407(a), 7410. After public notice and
hearings, a state must adopt the SIP and submit it to EPA for


    1
   Because EPA must reconsider the two plans and only approve them
with the necessary measures included, we need not reach Petitioners’ other
arguments, which Petitioners are free to raise again after EPA’s
reconsideration and subsequent final action.
    2
        All citations to the United States Code refer to the 2012 edition.
            COMM. FOR A BETTER ARVIN V. EPA                  7

review and approval. Id. § 7410(a). EPA must then act on
the SIP, approving or disapproving it in part or in whole.
42 U.S.C. § 7410(k)(3). Once approved by EPA, a “SIP
bec[o]me[s] federal law . . . , and c[annot] be changed unless
and until EPA approve[s] any change.” Safe Air for Everyone
v. EPA, 488 F.3d 1088, 1097 (9th Cir. 2007) (emphasis
omitted). The CAA provides a private right of action for
citizens to enforce a SIP by bringing a civil action in federal
district court. 42 U.S.C. § 7604.

                              B

    The CAA also regulates mobile source emissions, such as
those from cars and trucks. Congress has generally
preempted states from setting mobile source emissions
standards. Jensen, 644 F.3d at 938 (citing 42 U.S.C.
§ 7543(a)). California, however, may set its own mobile
source emissions standards, with EPA approval. Id. at 938
n.3 (citing 42 U.S.C. § 7543(b) (motor vehicles); § 7543(e)(2)
(nonroad sources)). California thus relies on its own mobile
source standards in the development of its SIPs.

                              C

    The present challenge relates to EPA’s approval of
revisions to California’s 2007 SIP, and specifically to plans
for achieving compliance with national standards for two
pollutants: fine particulate matter (“PM2.5”) and ozone.

    In 1997, EPA promulgated 24-hour and annual standards
for PM2.5. The relevant parts of California’s plan to meet
these requirements are: (1) the District’s 2008 PM2.5 Plan,
revised in 2010 and 2011; and (2) provisions of CARB’s
2007 State Strategy, as revised in 2009 and 2011, that relate
8          COMM. FOR A BETTER ARVIN V. EPA

to the San Joaquin Valley (collectively, “the PM2.5 Plan”).
The PM2.5 Plan was proposed for inclusion in California’s
SIP. On November 9, 2011, EPA approved in part and
disapproved in part the PM2.5 Plan in a final rulemaking, and
the timely petition for review in case number 11-73924
followed.

    As to ozone, EPA promulgated the 8-hour ozone standard
to replace the 1-hour standard in 1997, and adopted a more
stringent 8-hour ozone standard in 2008. The 8-hour standard
refers to the average concentration of ground-level ozone,
which can contribute to lung disease, as measured over an 8-
hour period in a given area. The key parts of California’s
plan to meet the 8-hour ozone standard are: (1) the District’s
2007 Ozone Plan, as revised in 2008 and 2011; and (2) the
provisions of CARB’s State Strategy, as revised in 2009 and
2011, that pertain to the San Joaquin Valley (collectively,
“the 8-Hour Plan”). EPA approved the 8-Hour Plan on
March 1, 2012, and the timely petition for review in case
number 12-71332 followed.

    We refer collectively to the PM2.5 and 8-Hour Plans as
“the Plans.” Because the two petitions are closely related and
involve the same parties, we address the petitions together.

                              II

    We have jurisdiction to review EPA’s action pursuant to
42 U.S.C. § 7607(b)(1). We review approval of a SIP by
considering whether the EPA’s decision was arbitrary,
capricious, an abuse of discretion, or contrary to law. Sierra
Club v. EPA, 671 F.3d 955, 961 (9th Cir. 2012) (noting that
when assessing CAA challenges, we apply the general
standard of review for agency decisions set forth in the
           COMM. FOR A BETTER ARVIN V. EPA                 9

Administrative Procedure Act, 5 U.S.C. §§ 701–06). “With
respect to the CAA, Congress has given EPA general
rulemaking authority, 42 U.S.C. § 7601(a)(1), which, when
exercised, requires our deference in accordance with
Chevron.” Id. at 962.

       Chevron, U.S.A., Inc. v. Natural Res. Def.
       Council, Inc., 467 U.S. 837 (1984)[,]
       generally sets forth the framework by which
       we review an agency’s interpretation of a
       statute. Id. at 842–44. Under this framework
       at the first step we determine “whether
       Congress has directly spoken to the precise
       question at issue. If the intent of Congress is
       clear, that is the end of the matter; for the
       court, as well as the agency, must give effect
       to the unambiguously expressed intent of
       Congress.” Id. at 842–43. “[I]f the statute is
       silent or ambiguous with respect to the
       specific issue, the question for the court is
       whether the agency’s answer is based on a
       permissible construction of the statute.” Id. at
       843.

Sierra Club, 671 F.3d at 961–62. EPA’s interpretation of its
own regulations is given considerable deference and “must be
given controlling weight unless it is plainly erroneous or
inconsistent with the regulation.” Thomas Jefferson Univ. v.
Shalala, 512 U.S. 504, 512 (1994) (internal quotation marks
omitted); see also Auer v. Robbins, 519 U.S. 452, 461 (1997).
10          COMM. FOR A BETTER ARVIN V. EPA

                             III

                              A

    Because the language and structure of the CAA demand
that all control measures on which the Plans rely to attain the
NAAQS be included in the SIP and subject to enforcement by
individuals and by EPA, we grant the petition for review in
part.

    As explained above, the CAA makes “the regulation of
mobile source emissions . . . a federal responsibility, [and]
Congress has expressly preempted states from setting
emissions standards for mobile sources.” Jensen, 644 F.3d at
938 (citing 42 U.S.C. § 7543). “The notable exception to this
general rule is that California is permitted to set its own
mobile emissions standards so long as it obtains EPA
approval.” Id. at 938 n.3 (citing 42 U.S.C. § 7543). Once
approved, these state-adopted measures (“waiver measures”),
which are more stringent than federal alternatives, allow the
state to avoid the preemptive federal emissions standards. 42
U.S.C. § 7543(b).

    A SIP must “include enforceable emission limitations and
other control measures . . . as may be necessary or appropriate
to meet the applicable requirements of this chapter.” Id.
§ 7410(a)(2)(A). The CAA provides a private right of action
for citizens to enforce a SIP’s provisions through a civil
action in federal court, 42 U.S.C. § 7604, but only those
provisions actually included in the SIP are subject to such
enforcement, see El Comite Para El Bienestar de Earlimart
v. Warmerdam, 539 F.3d 1062, 1069–70 (9th Cir. 2008).
            COMM. FOR A BETTER ARVIN V. EPA                  11

    Here, the Plans’ control strategies are based in significant
part on reductions that will be achieved through waiver
measures, which allow consideration of the stricter state
standards rather than federal standards. Thus, although EPA
approved the waiver measures such that they are not subject
to federal preemption, 42 U.S.C. § 7543, EPA approved the
Plans at issue here without including those waiver measures
on which the State’s strategy to comply with the NAAQS for
PM2.5 and 8-hour ozone partially relied. Petitioners argue that
in so doing, EPA violated the plain terms of the CAA. We
agree.

     EPA acknowledges that the Plans rely in part on waiver
measures but argues that because of EPA’s longstanding
policy of not requiring waiver measures to be specifically
included in California SIPs and because of Congress’s alleged
ratification of that practice under the so-called “savings
clause” in the CAA, see 42 U.S.C. § 7515, the CAA does not
require waiver measures, which have already been subject to
an EPA approval process, to undergo an additional approval
process by being included in a SIP.

    But, to the contrary, the plain language of § 7410(a)
refutes EPA’s position. The statute makes clear that SIPs
“shall include” all emissions limitations, control measures,
means, and techniques on which the state relies to assure
compliance with the CAA. 42 U.S.C. § 7410(a)(2)(A)
(emphasis added). The language associated with “include” is
mandatory. Moreover, the phrase “necessary or appropriate
to meet the applicable requirements of this chapter” refers to
the CAA as a whole (a chapter of Title 42 of the U.S. Code,
rather than the section relating to SIPs). 42 U.S.C. § 7410(a).
There is no viable justification for reading this section to
simply permit, rather than affirmatively mandate, a SIP to
12          COMM. FOR A BETTER ARVIN V. EPA

include all measures required to achieve compliance with the
NAAQS. Instead, common sense tells us that a SIP must
include waiver measures to the extent that they are needed to
achieve a state’s compliance with the federally required air
quality standards.

    As for EPA’s ratification argument, the CAA’s savings
clause states in relevant part:

        Each regulation, standard, rule, notice, order
        and guidance promulgated or issued by the
        Administrator under this chapter, as in effect
        before November 15, 1990, shall remain in
        effect according to its terms, except to the
        extent otherwise provided under this chapter,
        inconsistent with any provision of this
        chapter, or revised by the Administrator.

Id. § 7515 (emphasis added). The plain language of this
section says that only official policies set forth in a pre-1990
regulation, standard, rule, notice, order, and guidance, and
that are not inconsistent with the CAA remain in effect. But,
as noted, the EPA’s interpretation that waiver measures need
not be included in SIPs does contradict the plain language of
§ 7410(a). Because the meaning of the statutory language is
clear, it is unnecessary to consider whether EPA’s
interpretation is reasonable. See Chevron U.S.A., Inc. v.
NRDC, Inc., 467 U.S. 837, 842–43 (“If the intent of Congress
is clear, that is the end of the matter; for the court, as well as
the agency, must give effect to the unambiguously expressed
intent of Congress.”).

   This plain language reading is further supported by the
most basic of principles. If the state standards that are
            COMM. FOR A BETTER ARVIN V. EPA                 13

necessary for meeting federal requirements are not a part of
the SIP, then, while the state agency, CARB, perhaps could
enforce them, the responsible federal agency, EPA, would not
be able to bring an action directly challenging violation of
those state standards. It is the primary responsibility of EPA
to ensure that Congress’s aims to ensure healthy air quality
have been carried out, and it is fundamentally error if any of
the standards necessary for federal compliance are not within
the SIP so as to be enforceable directly by the responsible
federal agency. The federal agency, EPA, not the state
agency, CARB, has the fundamental duty to carry the ball
across the goal line to achieve compliant air quality levels or
satisfactory progress toward that end.

    EPA’s interpretation of the savings clause as ratifying its
practice of approving California’s SIPs without subjecting the
waiver measures to review when the SIP is approved is also
inconsistent with citizens’ private right of action to enforce
SIP provisions. See 42 U.S.C. § 7604. Citizens cannot
enforce provisions that are not a part of the SIP. EPA in its
briefing concedes that its interpretation would prevent both
citizens and EPA itself from enforcing the California’s waiver
measures under the CAA in the context of a SIP “because
they are not in the SIP.” EPA argues, however, that citizens
have recourse under the CAA to enforce federal standards,
and that CARB itself can enforce the waiver measures. But
this frustrates congressional intent as expressed in the CAA’s
provision of a private right of action through which citizens
may enforce SIPs and their constituent parts, and not merely
enforce federal baseline standards for emissions generally.
Also, as Petitioners point out, the federal standards are less
stringent than California’s standards. This means that the SIP
provisions themselves, which depend on the more stringent
waiver measures, can be only incompletely enforced by
14          COMM. FOR A BETTER ARVIN V. EPA

citizens in federal court, insofar as emission reductions in the
Plans depend on reductions created by the gap between
federal measures and the waiver measures.

    Having any state law standards that are necessary for
compliance with the federal law requirements incorporated as
part of the SIP, so as to be directly enforceable by EPA and
by citizens, is a more safe and sensible system of enforcement
than that urged by EPA. We conclude that the enforcement
gap for private citizens and EPA in the present SIP is
inconsistent with the CAA’s requirements and the express
aims of Congress. Because the plain language of the CAA
does not support EPA’s interpretation that waiver measures
need not be included in SIPs that depend on them, we
conclude that EPA violated the CAA by approving the Plans
without the inclusion of the waiver measures on which they
relied.

                               B

    Petitioners also contend that EPA erred when it did not
require the Plans to include so-called “non-waiver measures.”
These are other state enforcement measures that are not a part
of the SIP but that Petitioners claim are also needed to meet
attainment standards. For the reasons explained below, we
reject this challenge.

   Specifically, Petitioners challenge EPA’s failure to
require the SIP to include three non-waiver measures: (1) the
Heavy Duty Diesel Engine-Chip Reflash measure; (2) the
Diesel Particulate Matter Control Measure for On-Road
Heavy-Duty Diesel-Fueled Vehicles Owned or Operated by
Public Agencies and Utilities (“Diesel Particulate Matter
Rule”); and (3) the Solid Waste Collection Vehicle Rule.
             COMM. FOR A BETTER ARVIN V. EPA                        15

    Regarding the Heavy Duty Diesel Engine-Chip Reflash
measure, EPA explains that because that rule was partially
invalidated by the California Supreme Court and repealed
four years before EPA approved the PM2.5 Plan, that rule
could not have been included in the PM2.5 Plan. See Approval
of 2008 San Joaquin Valley PM2.5 Plan and 2007 State
Strategy, 76 Fed. Reg. 69,896, 69,908 (Nov. 9, 2011) (to be
codified at 40 C.F.R. pt. 52) (noting that any emissions
reduction credit related to diesel engine chip reflashes were
from those vehicles whose engine chips were “reflashed”
before the rule was invalidated and adding that attempts to
invalidate those “reflashes” could be prosecuted under CAA
anti-tampering provisions). EPA did not give emission
reduction credit based on the chip reflash rule itself, but
instead based on actions taken under the rule before the
California Supreme Court invalidated it. Petitioners’
argument related to this non-waiver measure fails.

    Regarding the Diesel Particulate Matter Rule and the
Solid Waste Collection Vehicle Rule, EPA did not approve
those mobile source measures into the Plans because their
overall emission reduction effects were de minimis and did
not affect EPA’s overall evaluations of California’s ability to
meet the relevant air quality standards by the statutory
deadline. See id.

    We have applied in statutory interpretation the ancient
principle that the law does not care about trifles. See, e.g.,
Skaff v. Meridien N. Am. Beverly Hills, LLC, 506 F.3d 832,
839–40 (9th Cir. 2007).3 We conclude that the CAA allows


  3
    In Skaff we pointed to both the substance of the Latin maxims de
minimis non curat lex and lex non curat de minimis, and also cases in
which those principles had been applied by English and American courts,
16           COMM. FOR A BETTER ARVIN V. EPA

EPA to ignore trifling emission control measures when EPA
evaluates SIPs. Here, EPA has urged that these state law
measures were not included in the SIP because they had no
measurable impact on California’s ability to meet required air
quality levels. We cannot say on the record before us that
EPA’s conclusion that these standards have de minimis
impact on the relevant issue is arbitrary and capricious, or
contrary to law. See 5 U.S.C. § 706(2)(A). Further, the CAA
requires SIPs to include any of a variety of enforceable
emission control measures “as may be necessary or
appropriate” to meet the CAA’s general requirements.
42 U.S.C. § 7410(a)(2). This language implies that some
emission control measures may not be necessary or
appropriate to meet the CAA’s requirements—although, as
we held above, those measures upon which compliance plans
rely must be included. EPA expressly stated that when it
approved the Plans, it determined that the Diesel Particulate
Matter Rule and the Solid Waste Collection Vehicle Rule
produced only de minimis emission reductions and so did not
affect EPA’s overall attainment and reasonable further
progress evaluations. Approval of 2008 San Joaquin Valley
PM2.5 Plan and 2007 State Strategy, 76 Fed. Reg. 69,896
69,908 (Nov. 9, 2011) (to be codified at 40 C.F.R. pt. 52).
Those two rules, then, were not necessary or appropriate to
meet the CAA’s requirements according to EPA, and EPA
did not err in approving the Plans without incorporating these
emission control measures. We conclude that EPA’s decision
not to approve the three specific non-waiver measures into
the Plans was not arbitrary or capricious and did not violate
the CAA.




including the United States Supreme Court. 506 F.3d at 839–40.
            COMM. FOR A BETTER ARVIN V. EPA                 17

                              IV

    The control strategies for both Plans in part rely on state
commitments to propose and adopt emission control
measures and to achieve aggregate emission reductions
sufficient to comply with the NAAQS. The CAA does not
specifically address commitments by states to propose or
adopt emission control measures or to achieve additional
emissions reductions. See BCCA Appeal Grp. v. EPA,
355 F.3d 817, 839–40 (5th Cir. 2003). But the CAA does
allow a variety of “other control measures, means, or
techniques . . . as well as schedules and timetables for
compliance” to comprise an enforceable control strategy. Id.
at 839; see also 42 U.S.C. § 7410(a)(2)(A). Where EPA has
previously relied on such commitments, courts have upheld
their inclusion in SIPs. See BCCA, 355 F.3d at 838 n.25
(collecting cases); Envtl. Def. v. EPA, 369 F.3d 193, 209 (2d
Cir. 2004).

    Petitioners do not challenge the validity of enforceable
commitments generally. Instead, they argue that California’s
commitments to propose and adopt emission control
measures and to achieve aggregate emission reductions are
merely aspirational goals and are unenforceable, because they
contain no specific strategies or measures, and they
impermissibly allow specific measures to fail to meet their
individual emission reduction targets so long as the aggregate
emission reduction commitment is met. Alternatively,
Petitioners argue that even if the commitments are not merely
aspirational goals, they are still unenforceable because:
(1) California has discretion whether to change or honor
them; and (2) it is practically impossible to bring a timely
enforcement action if commitments remain unfulfilled by
their deadlines. We reject these arguments and conclude that
18          COMM. FOR A BETTER ARVIN V. EPA

California’s commitments are enforceable. EPA’s approval
of the commitments to propose and adopt emission control
measures and to achieve aggregate emission reductions was
not arbitrary or capricious and did not violate the CAA.

                              A

    Petitioners analogize California’s commitments to
achieve aggregate emission reductions to the public transit
ridership target in Bayview Hunters Point Community
Advocates v. Metropolitan Transportation Commission,
where we held that a “target” to increase ridership by 15%
was not a binding obligation and could not be enforced
against the public transportation agency. 366 F.3d 692, 695
(9th Cir. 2004). But the analogy fails. In Bayview, our
conclusion that the ridership target was an unenforceable goal
relied on two primary aspects of the transportation control
measure at issue—its language and logic. Id. First, we noted
that nothing in the transportation control measure’s language
actually required a ridership increase by any amount, and that
instead, the “expected ridership increase was never described
as anything more than a ‘target[.]’” Id. at 698. The word
“target” was significant, because agreeing to establish one
was “not the same as promising to attain” that ridership
increase. Id. Here, however, the Plans use mandatory and
non-discretionary language to “commit[] . . . to adopt[ing]
and implement[ing] measures that will achieve specific
[emissions] reductions by specific years.” Approval of 8-
Hour Ozone Plan for San Joaquin Valley, 77 Fed. Reg.
12,652, 12,653–54 (Mar. 1, 2012) (to be codified at 40 C.F.R.
pt 52); see 40 C.F.R. § 52.220(c)(356)(ii)(B)(2) and (4),
(392)(ii)(A)(2), (395)(ii)(A)(2), (397)(ii)(B)(2) (codifying by
reference both CARB’s and the District’s commitments to
propose and adopt emission control measures by specific
            COMM. FOR A BETTER ARVIN V. EPA                 19

years and to achieve specific amounts of aggregate emission
reductions by specific years). The language differences
between the ridership target in Bayview and California’s
commitments here support the conclusion that California’s
commitments are not merely aspirational goals.

    Second, we concluded in Bayview that the ridership target
relied on “hoped-for increases in productivity” to boost public
transit use. Bayview, 366 F.3d at 698. But predicting public
human behavior is unreliable. Id. at 699. Here, by contrast,
state commitments to propose and adopt emission control
measures require government agency action, not action by the
public. Commitments by the state of California to reduce
aggregate emissions reductions by specially tailored methods
are reasonably within the control of state agencies. The idea
that the public transportation agency in Bayview might
control ridership increases “impli[ed] the implausible
proposition” that a “target” for anticipated public
participation compelled compliance. Id. But the idea that
California here can and will propose and adopt emission
control measures and achieve aggregate emission reductions
by specific amounts and within specific time-frames is
plausible and consistent with commitments by other states
that other circuits have upheld. See BCCA, 355 F.3d at 841
(upholding EPA’s approval, into the Houston, Texas SIP, of
commitments to adopt and implement additional emission
controls on a fixed schedule and to achieve additional
emission reductions); Envtl. Def., 369 F.3d at 209–10
(upholding EPA’s approval of enforceable commitments into
New York’s one-hour ozone SIP). Because the commitments
in both Plans require California to meet specific reductions by
specific deadlines, we conclude that California’s
commitments to propose and adopt emission control
20          COMM. FOR A BETTER ARVIN V. EPA

measures and to achieve aggregate emission reductions are
not merely aspirational, unenforceable goals.

                              B

    Alternatively, Petitioners argue that even if California’s
commitments to achieve aggregate emission reductions are
not merely aspirational goals, they remain unenforceable
because: (1) California has ultimate discretion to determine
whether the aggregate emission reduction commitments are
met; and (2) enforcement is impractical because it is
“virtually impossible” to determine, based on limited and
difficult-to-access information, whether California has met its
aggregate emission reduction commitments. Even if citizens
could access such information, Petitioners argue,
“enforcement would be delayed until it was too late to meet
the attainment deadline.” We disagree.

    Petitioners’ discretion argument focuses on the way
California calculates the amount of emission reductions it
must achieve to meet the relevant NAAQS and on
California’s determinations whether adopted emission control
measures actually achieve claimed reductions. Petitioners
contend that by reducing the baseline inventory, which is an
estimate of future emissions assuming no control strategies
are adopted, California can claim that fewer or less stringent
control measures than those approved in the SIP are required
to reduce emissions to the necessary levels.

    While we did conclude in Warmerdam that neither a
baseline inventory nor the methodology used to calculate it is
independently enforceable, 539 F.3d at 1072–73, that does
not mean that California’s emissions reduction strategies here
are unenforceable. The reason is simple: Once approved into
            COMM. FOR A BETTER ARVIN V. EPA                 21

a SIP, the measures and the emissions reduction
requirements, as well as the relevant deadlines, are binding on
the state, and can only be altered through a SIP revision
approved by EPA in another notice-and-comment
rulemaking. See 42 U.S.C. § 7410(l); 5 U.S.C. § 553.
Moreover, EPA may not approve any SIP revision that would
interfere with California’s ability to meet the air quality
requirements. 42 U.S.C. § 7410(l). Even if California sought
to revise its commitments, it would need to obtain EPA’s
approval, which could only be forthcoming following a
notice-and-comment period in which Petitioners could
participate.

    Finally, Petitioners argue that California’s commitments
to propose and adopt emission control measures and to
achieve aggregate emission reductions are unenforceable as
a practical matter, because “EPA and citizens would be left
to determine, based on information exclusively held and
maintained by CARB and the District” whether the state
agencies have fulfilled their commitments. Petitioners further
contend that even if one could determine whether California’s
commitments were fulfilled, such a determination could not
be made until after milestone dates and shortly before the
attainment deadline, which in turn would delay enforcement
and remedy until “well after the attainment date.” We reject
Petitioners’ practicality argument.

    For support, Petitioners cite EPA’s published fundamental
principles for effective SIPs and control strategies. One of
these principles is enforceability, which requires that SIPs
(1) be “duly adopted, and specify clear, unambiguous, and
measurable requirements”; (2) contain a “legal means for
ensuring that sources [comply] with the control measure”;
and (3) be “enforceable in practice.” State Implementation
22             COMM. FOR A BETTER ARVIN V. EPA

Plans, 57 F3d. Reg. 13,498, 13568 (proposed Apr. 16, 1992)
(to be codified at 40 C.F.R. pt. 52). Specifically, a
“regulatory limit is not enforceable if, for example, it is
impractical to determine compliance with the published
limit.” Id. Petitioners fail to show how California’s
commitments fall short of this standard. As EPA and the
District explain, the information that Petitioners contend is so
difficult to know or retrieve is readily available throughout
the regulatory processes preceding adoption of emission
control measures into the SIP. See Cal. Gov’t Code
§§ 11340, 11343–49.6 (listing notice and information
requirements for California agencies when considering and
adopting regulations); Cal. Health & Safety Code
§§ 40725–28.5 (listing public hearing and record
requirements for rules or regulations to be considered and
adopted by California Air Pollution Control Districts).4
CARB itself prepares assessments of the potential for
significant environmental impacts of proposed regulations.
Cal. Code Regs. tit. 17, § 60005 (2015). CARB and the
District must also analyze “reasonably foreseeable methods”
for how compliance will be achieved with certain
environmental regulations. Cal. Code Regs. tit. 14, § 15187
(2015). And EPA’s own notice-and-comment rulemaking
procedures to determine whether measures will receive SIP
credit present another opportunity for citizens to track the
development of emission control measures. Aside from
information available from or produced as a result of
administrative rulemaking at the state and federal levels, the
public can also seek information within the control of
California agencies through the California Public Records
Act. See Cal. Gov’t Code §§ 6250–6276.48. We conclude
that California’s commitments to propose and adopt emission

 4
     All citations to the California Code refer to the West 2014 edition.
            COMM. FOR A BETTER ARVIN V. EPA                  23

control measures and to achieve aggregate emission
reductions are not unenforceable for lack of publicly available
information.

    We also conclude that Petitioners can seek timely
remedies under the CAA if California does not fulfill its
commitments to propose and adopt emission control
measures or to achieve aggregate emission reductions.
Because the public cannot sue to enforce a commitment until
after a commitment deadline has passed does not negate a
commitment’s enforceability. As EPA notes, this argument
conflates enforcing specific commitments, which would be
independently enforceable emission control measures in a
SIP, with the more general requirement that states attain
national air quality standards by specific dates. We decline
to extend the CAA’s citizen-suit provision beyond what it
says by providing for general attainment-forcing remedies
when the CAA does not. See 42 U.S.C. § 7604(a)
(authorizing citizen suits to obtain remedies for, among other
things, violations of “emission standard[s] or limitation[s].”).
If California does not fulfill a commitment to propose and
adopt emission control measures or to achieve aggregate
emission reductions, the public can seek a remedy for such
specific violations. If, on the other hand, California does not
attain required air quality standards, EPA may use means
available under other parts of the CAA to ensure that the state
attains the relevant national air quality standard. See, e.g.,
42 U.S.C. §§ 7413, 7509.

   Because California’s commitments to propose and adopt
emission control measures and to achieve aggregate emission
reductions are neither aspirational goals nor unenforceable as
a matter of discretion or practicality, we conclude that these
commitments are enforceable emission standards or
24         COMM. FOR A BETTER ARVIN V. EPA

limitations, and that EPA’s approval of them into the Plans
was not arbitrary or capricious and did not violate the CAA.
We deny this portion of the petition for review.

                             V

   We grant the petition for review in part and remand the
matter to EPA for further proceedings consistent with our
decision.

    Petitioners may recover from EPA the costs and fees
incurred in this litigation.        42 U.S.C. § 7607(f).
Determination of an appropriate amount of fees and costs is
referred to the Appellate Commissioner, who shall conduct
whatever proceedings he deems appropriate, and who shall
have authority to enter an order awarding the same. See Ober
v. EPA, 84 F.3d 304 316 (9th Cir. 1996).

  PETITION GRANTED in part, DENIED in part, and
REMANDED.
