FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

SAFE AIR FOR EVERYONE; AMERICAN 

LUNG ASSOCIATION OF IDAHO; NOËL

STURGEON,

Petitioners,

v. No. 05-75269

UNITED STATES ENVIRONMENTAL EPA No.

PROTECTION AGENCY; STEPHEN L. ID-03-003

JOHNSON, Administrator of the

United States Environmental  ORDER

Protection Agency; ELIN D. AMENDING

MILLER,* Regional Administrator OPINION AND

of the United States AMENDED

Environmental Protection Agency, OPINION

Region X,

Respondents,

STATE OF IDAHO,

Intervenor. 

On Petition for Review of an Order of the

Environmental Protection Agency

Argued and Submitted

November 15, 2006—Seattle, Washington

Filed January 30, 2007

Amended May 29, 2007

*Elin D. Miller is substituted for her predecessor as Regional Administrator of the United States Environmental Protection Agency. Fed. R. App.

P. 43(c)(2). 

6265
Before: Arthur L. Alarcón, Pamela Ann Rymer, and

Marsha S. Berzon, Circuit Judges.

Opinion by Judge Berzon

6266 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
COUNSEL

David S. Baron, Earthjustice, Washington, D.C., for the petitioners. 

Paul Cirino, Environmental Defense Section, U.S. Department of Justice, Washington, D.C., for the respondents. 

Lisa J. Kronberg, Deputy Attorney General, Idaho Department of Environmental Quality, Boise, Idaho, for the intervenor. 

6268 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
ORDER

Petitioners’ Petition for Clarification is GRANTED. The

opinion filed on January 30, 2007 and reported at 475 F.3d

1096 is hereby amended as follows: 

1) On 475 F.3d at 1099, the sentence beginning “Because

our review . . .” is replaced with: “Because our review of an

administrative agency’s decision begins and ends with the

reasoning that the agency relied upon in making that decision,

see SEC v. Chenery Corp., 318 U.S. 80, 87, 63 S.Ct. 454, 87

L.Ed. 626 (1943); Ctr. for Biological Diversity v. Kempthorne, 466 F.3d 1098, 1103-04 (9th Cir. 2006), we grant the

petition for review, vacate EPA’s approval of the amendment,

and remand for EPA’s reconsideration of SAFE’s objections

under a correct understanding of the preexisting Idaho SIP.”

2) On 475 F.3d at 1099, the sentence beginning “Finally,

we explain why our interpretation . . .” is replaced with: “Finally, we explain why our interpretation of the SIP as it

existed at the time of the 2005 amendment resolves this case

and requires that we grant the petition for review, vacate

EPA’s approval of the amendment, and remand for further

proceedings.” 

3) On 475 F.3d at 1109-10, the sentence beginning “We

therefore grant . . .” is replaced with: “We therefore grant

SAFE’s petition, vacate EPA’s approval of the amendment,

and remand to EPA for its consideration of Idaho’s proposed

amendment as a change in the preexisting SIP, rather than as

simply a “clarification” of it.” 

4) On 475 F.3d at 1110, the final line of the opinion is

changed to: “Petition for Review GRANTED; EPA’s

approval VACATED; REMANDED to EPA.” 

Petitioners’ Petition for Panel Rehearing is DENIED as

moot. No further petitions for rehearing or rehearing en banc

will be accepted.

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6269
OPINION

BERZON, Circuit Judge: 

The Clean Air Act (“CAA” or “the Act”), 42 U.S.C.

§§ 7401-7671q, authorizes the creation of air quality standards for a number of pollutants, including particulate matter

produced as a byproduct of burning. To implement these standards, the Act establishes a system of State Implementation

Plans (“SIPs”), whereby states submit, subject to the United

States Environmental Protection Agency’s (“EPA”) review

and approval, proposed methods for maintaining air quality.

Once approved by EPA these plans “[h]av[e] ‘the force and

effect of federal law.’ ” Trs. for Alaska v. Fink, 17 F.3d 1209,

1210 n.3 (9th Cir. 1994) (quoting Union Elec. Co. v. EPA,

515 F.2d 206, 211 (8th Cir. 1975), aff’d, 427 U.S. 246

(1976)). 

In this case, we are presented with a preexisting SIP containing language that prohibits open burning generally and

contains no exception allowing farmers to burn the residue

left in their fields after harvesting their crops. Petitioner, Safe

Air for Everyone (“SAFE”), challenges EPA’s decision to

approve an amendment to that SIP authorizing such burning.

SAFE argues that certain CAA provisions which prohibit

amending SIPs so that they interfere with meeting air quality

standards forbid EPA’s action, at least absent further analysis

of field burning’s impact on Idaho’s air quality; EPA maintains that its approval of the amendment does not contravene

any CAA provisions. 

We hold that as it presently stands, EPA’s approval is

legally unsustainable. EPA grounded its approval of this

amendment on the premise that the preexisting Idaho SIP did

not ban field burning, so that the amendment only clarified

what was already the case. This view of the preexisting SIP

is one with which we cannot agree. Because our review of an

administrative agency’s decision begins and ends with the

6270 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
reasoning that the agency relied upon in making that decision,

see SEC v. Chenery Corp., 318 U.S. 80, 87, 63 S.Ct. 454, 87

L.Ed. 626 (1943); Ctr. for Biological Diversity v. Kempthorne, 466 F.3d 1098, 1103-04 (9th Cir. 2006), we grant the

petition for review, vacate EPA’s approval of the amendment,

and remand for EPA’s reconsideration of SAFE’s objections

under a correct understanding of the preexisting Idaho SIP. 

The current treatment of field burning in the Idaho SIP

came about as the result of a thirty-five-year regulatory evolution. After reviewing the factual administrative record, we

first explain the regulatory process established by the CAA

and then trace the development of the current SIP provisions

related to field burning in Idaho. We then closely examine

how the preexisting Idaho SIP treated field burning prior to

2005, when EPA approved an amendment to the SIP that

explicitly authorized the practice. Finally, we explain why our

interpretation of the SIP as it existed at the time of the 2005

amendment resolves this case and requires that we grant the

petition for review, vacate EPA’s approval of the amendment,

and remand for further proceedings.

I.

A.

Open burning of agricultural fields is a common practice in

Idaho, particularly among bluegrass farmers in the northern

portion of the state. Those farmers maintain that burning the

grass residue improves the productivity of their fields and has

certain environmental benefits, views with which the Idaho

legislature has expressed agreement. See IDAHO CODE ANN.

§ 22-4801 (2006) (“The legislature finds that the current

knowledge and technology support the practice of burning

crop residue to control disease, weeds, pests, and to enhance

crop rotations. . . . The legislature finds that due to the climate, soils, and crop rotations unique to north Idaho counties,

crop residue burning is a prevalent agricultural practice and

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6271
that there is an environmental benefit to protecting water

quality from the growing of certain crops in environmentally

sensitive areas.”); Safe Air for Everyone v. Meyer, 373 F.3d

1035, 1043-47 (9th Cir. 2004) (recognizing that “the Growers

realize farming benefits from reusing grass residue in the process of open burning”). 

Despite these attested benefits, the administrative record

establishes that such field burning is also a source of particulate matter that contributes to air pollution. SAFE submitted

evidence indicating that the burning of agricultural fields in

Idaho creates significant air quality problems. That evidence

documents: (1) that clouds of smoke cover large portions of

rural Idaho and surrounding states during burning season; (2)

that area doctors believe that this smoke has had particularly

severe health consequences for individuals with respiratory

ailments; (3) that some individuals with such ailments have

fled their homes during burning season to avoid the smoke;

and (4) that a coroner’s report linked at least one fatality to

field burning. EPA has recognized that substantial pollution

and health problems are created by the practice. See EPA,

AGRICULTURAL BURNING: EPA MAKES NORTHWEST FIELD BURNING A TOP PRIORITY 2 (2000) (“[F]ield burning can cause serious environmental and health effects. . . . Scientific studies —

along with thousands of complaints — indicate that smoke is

unhealthy. . . . Exposure to fine particles, either alone or combined with other air pollutants, has been linked to difficulty

in breathing, aggravated asthma, increased emergency room

visits and hospital admissions, and, in some cases, premature

deaths.”). 

B.

Under the CAA, EPA has the authority to issue national air

quality standards setting the maximum allowable concentration of a given pollutant. 42 U.S.C. § 7409(a).1

 Using this

1All citations to the United States Code refer to the 2000 edition, unless

noted otherwise. 

6272 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
authority, EPA has issued limits for particulate matter. 40

C.F.R. §§ 50.6, 50.7. 

To assure that such air quality standards are met, the CAA

establishes a system heavily dependant upon state participation. See 42 U.S.C. § 7407(a) (“Each State shall have the primary responsibility for assuring air quality within the entire

geographic area comprising such State . . . .”); see generally

Train v. Natural Res. Def. Council, 421 U.S. 60, 64-70

(1975). As a central aspect of this system, states promulgate

SIPs that “provide[ ] for implementation, maintenance, and

enforcement” of the CAA’s air quality standards within the

state. 42 U.S.C. § 7410(a)(1). Although states retain significant flexibility in establishing the details of these plans, the

CAA, and EPA regulations, outline many required features.

Id. § 7410(a)(2) (6); 40 C.F.R. pt. 51. Among them is the

mandate that state plans provide for regular revisions to

reflect evolving air quality conditions and standards. 42

U.S.C. § 7410(a)(2)(H). These revisions need not be wholesale recastings of SIPs; instead, the CAA allows the states to

submit, and EPA to review, piecemeal amendments dealing

with discrete SIP provisions, leaving most of the plan

untouched. See Hall v. U.S. EPA, 273 F.3d 1146, 1159-60

(9th Cir. 2001). 

Before a SIP becomes effective, EPA must determine that

it meets the CAA’s requirements. 42 U.S.C. § 7410(k)(3).

EPA must also approve plan amendments and “shall not

approve a revision of a plan if the revision would interfere

with any applicable requirement concerning attainment and

reasonable further progress . . . or any other applicable

requirement of [the CAA].” Id. § 7410(l).

C.

Idaho, like every other state, was first required to submit a

SIP to EPA within thirteen months of the Act’s 1970 passage.

See Train, 421 U.S. at 65. The original Idaho SIP was

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6273
approved by EPA in May 1972. Approval and Promulgation

of Implementation Plans, 37 Fed. Reg. 10,842, 10,861 (May

31, 1972). A provision on open burning was among the Idaho

state regulations incorporated into that SIP: “No person shall

allow, suffer, cause or permit any open burning operation

which does not fall into at least one of the categories of Section 3.” Field burning was included in the types of burning

allowed by Section 3, but with significant limitations:

The open burning of plant life grown on the premises in the course of any agricultural, forestry, or

land clearing operation may be permitted when it can

be shown that such burning is necessary and that no

fire or traffic hazard will occur. Convenience of disposal is not of itself a valid necessity for burning.

1. It shall be the responsibility of any person conducting such burning to make every reasonable

effort to burn only when weather conditions are

conducive to a good smoke dissipation and only

when an economical and reasonable alternate

method of disposal is not available.

2. When such alternate method is made available,

it shall be put into use within a reasonable time.

3. Any person conducting an agricultural, forestry,

or land clearing burning operation similar to an

operation carried out by a governmental agency

shall follow the rules and procedures of the

agency with regard to minimizing air pollution.

4. When such burning creates air pollution or a

public nuisance, additional restrictions may be

imposed to minimize the effect upon the environment. 

6274 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
Section 3 also allowed eight other categories of open burning:

food preparation and recreational fires; weed control fires;

fires for firefighting training; industrial flares; residential

solid waste disposal fires in rural areas; disposal site fires;

junked motor vehicle fires; and orchard fires.2

In 1993, EPA approved amendments to the Idaho SIP that

substantially changed the open burning provisions. See

Approval and Promulgation of Implementation Plans, 58 Fed.

Reg. 39,445, 39,446 (July 23, 1993) (noting that in Idaho’s

submission, “the existing Rules for Control of Open Burning

and Categories of Allowable Burning were revised extensively” and that “[t]hese new and revised provisions for open

burning comply with EPA’s general requirements for SIP

control strategies” (citations omitted)). These SIP provisions,

incorporating section 01.01151.04(a) of Idaho air pollution

regulations in effect on December 31, 1991, contained a general prohibition on open air burning: 

No person shall allow, suffer, cause or permit any

open burning operation unless it is a category of

open burning set forth in Section 01.01153 and does

not include any of the following materials:

i. Garbage; 

ii. Dead animals or parts thereof; 

iii. Junked motor vehicles or any materials resulting from a salvage operation; 

2

In 1982, EPA approved amendments to Idaho’s SIP that incorporated

Idaho’s recodified air pollution regulations. See Approval and Promulgation of Implementation Plans, 47 Fed. Reg. 32,530, 32,531 (July 28,

1982). Those recodified regulations maintained the identical substantive

language of the open burning regulations incorporated into the 1972 SIP,

including the limited permission for field burning and permission for eight

other categories of fires. 

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6275
iv. Tires or other rubber materials or products; 

v. Plastics; 

vi. Asphalt or composition roofing or any other

asphaltic material or product; 

vii. Tar, tar paper, waste or heavy petroleum products, or paints;

viii. Lumber or timbers treated with preservatives; 

ix. Trade wastes except as allowed in Section

01.01153; 

x. Insulated wire; 

xi. Pathogenic wastes; or 

xii. Hazardous wastes.

(Emphases added). The revised regulation incorporated into

the SIP listed categories of allowable burning that no longer

included field burning. Instead, that list retained seven of the

nine categories of permitted fires included in the 1972 SIP

regulations — food preparation and recreational fires, weed

control fires, fires for firefighting training, industrial flares,

residential solid waste disposal fires in rural areas, disposal

site fires, and orchard fires; omitted two categories of permitted fires from the 1972 list — junked motor vehicle fires and

agricultural fires; and added three new categories of permitted

fires — prescribed burning, dangerous material fires, and

infectious waste burning. 

In 2003, EPA approved another set of Idaho SIP amendments. Those amendments incorporated updated versions of

Idaho regulations. This round of revisions, however, updated

the open burning regulations only to reflect a recodification.

6276 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
See Approval and Promulgation of Implementation Plans, 68

Fed. Reg. 2217, 2218 (Jan. 16, 2003) (“[S]ince EPA last

approved the Idaho SIP in 1993, Idaho has revised nearly

every section of its air quality rules to some degree. Many of

these amendments have been editorial and are renumberings,

changes to citations for cross-referenced rules or statutes,

changes in terminology, or grammatical corrections.”). The

substantive language of the incorporated provisions on open

burning was identical to the language approved in the 1993

SIP. 

That 2005 rulemaking approved amendments to the SIP

that added field burning as an eleventh category of allowed

burning. The relevant provision, incorporating section

58.01.01.617 of the Idaho Administrative Code in effect on

March 21, 2003, states: “The open burning of crop residue on

fields where the crops were grown is an allowable form of

open burning if conducted in accordance with the Smoke

Management and Crop Residue Disposal Act and the rules

promulgated pursuant thereto.” (Citations omitted). Although

Idaho first enacted statutes dealing with field burning in 1985

and amended them in 1986, 1999, and 2003, see Act of March

12, 1985, ch. 248, 1985 Idaho Sess. Laws 580 (codified as

amended at IDAHO CODE ANN. §§ 22-4801 to -4804 (2006)),

the SIP amendment approved by EPA in 2005 was the first

explicit reference to those statutes in the SIP, see Approval

and Promulgation of Air Quality Implementation Plan (“Final

SIP”), 70 Fed. Reg. 39,658, 39,659 (July 11, 2005) (noting

that the field burning legislation “was not [previously] specifically submitted to EPA as a SIP revision”).3

SAFE submitted comments to EPA during the 2005 rule3Although Idaho’s field burning statute was referenced in a 1993 report

submitted to EPA detailing Idaho’s strategy for bringing one portion of the

state into attainment with particulate matter pollution standards, that strategy did not purport to alter the provisions of Idaho’s statewide SIP, which

contains the language banning field burning. 

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6277
making process and now challenges EPA’s approval of the

amendment permitting field burning in this court. We have

jurisdiction over SAFE’s challenge to this 2005 rulemaking

under 42 U.S.C. § 7607(b)(1). This court reviews EPA’s decision to approve SIP amendments under the “arbitrary, capricious, or otherwise not in accordance with law” standard of

the Administrative Procedure Act (“APA”). Hall, 273 F.3d at

1155; see 5 U.S.C. § 706(2)(A).

II.

A.

As detailed above, Idaho’s 2003 SIP mandated that “[n]o

person shall allow, suffer, cause or permit any open burning

operation unless it is a category of open burning set forth” in

ten specified sections that “establish categories of open burning that are allowed when done according to the prescribed

conditions.” (Emphases added). Those ten sections cover:

“Recreational and Warming Fires”; “Weed Control Fires” for

“abatement along fence lines, canal banks, and ditch banks”;

“Training Fires” for firefighting training; “Industrial Flares”;

“Residential Solid Waste Disposal Fires”; “Landfill Disposal

Site Fires”; “Orchard Fires”; “Prescribed Burning” for fire

management purposes; “Dangerous Material Fires”; and “Infectious Waste Burning.” Field burning does not fit into any

of these categories. EPA so acknowledged during the 2005

rulemaking proceedings. See Final SIP, 70 Fed. Reg. at

39,659 (“EPA recognizes the rule language . . . does not, on

its face, appear to identify crop residue as a category of

allowed burning”); id. at 39,660 n.1 (noting EPA’s agreement

with SAFE that field burning does not come within the “prescribed burning” exception). Nor is it debatable that field

burning is an “open burning operation” covered by the SIP’s

expansive mandatory terms. 

In short, given the SIP’s broad prohibition and the absence

of any pertinent exception, the plain meaning of the SIP, in

6278 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
the clearest of terms, prohibits field burning. Cf. Craft v. Nat’l

Park Serv., 34 F.3d 918, 922 (9th Cir. 1994) (“[T]he regulation by its terms clearly prohibits appellants’ activities. With

two exceptions, the regulation prohibits ‘dredg[ing] or otherwise alter[ing] the seabed in any way.’ . . . There can be no

question but that this language prohibits the excavation activities in which appellants were engaged.” (second and third

alterations in original) (quoting 15 C.F.R. § 935.7(a)(2)(iii)

(1994))). 

[1] In interpreting a SIP, we begin with a look toward the

plain meaning of the plan and stop there if the language is

clear. This much is clear from Bayview Hunters Point Community Advocates v. Metropolitan Transportation Commission (BHPCA), 366 F.3d 692 (9th Cir. 2004), a leading case

in this court in which the meaning of a SIP was at stake. In

considering the SIP for the San Francisco Bay Area related to

transit ridership, BHPCA began by observing that “[w]e start

with the plain language of [the SIP]. ‘A regulation should be

construed to give effect to the natural and plain meaning of

its words,’ ” and then noted that “[t]he expected ridership

increase was never described as anything more than a ‘target.’ ” Id. at 698 (quoting Crown Pac. v. Occupational Safety

& Health Review Comm’n, 197 F.3d 1036, 1038 (9th Cir.

1999)). Because the plan did “not, on its face, require a ridership increase of 15%,” we held “[t]hat by its plain language

[the SIP] does not establish a mandatory requirement to

increase transit ridership by a specified percentage weighs

heavily against the conclusion that such an obligation can be

imposed based upon [the SIP].” Id. (internal quotation mark

omitted); see also Idaho Conservation League v. Boer, 362 F.

Supp. 2d 1211, 1216 (D. Idaho 2004) (refusing to defer to a

state environmental agency’s interpretation that “cannot be

reconciled with the plain language of the regulations”

included in the SIP); United States v. Gen. Dynamics Corp.,

755 F. Supp. 720, 723 (N.D. Tex. 1991) (“The [Texas state

agency’s] interpretation of the Texas SIP to allow plantwide

averaging is unreasonable, because it contradicts specific lanSAFE AIR FOR EVERYONE v. UNITED STATES EPA 6279
guage of the SIP . . . .”); Citizens for a Better Env’t v. Deukmejian, 731 F. Supp. 1448, 1454-55 (N.D. Cal. 1990)

(refusing to credit evidence that the provisions of a SIP did

not make a binding commitment when the SIP included “unequivocal[ ]” phrasing). Applying that same methodology

here, we would quite readily conclude that the pre-2005 Idaho

SIP did not permit field burning.

B.

[2] EPA, however, assumed during the 2005 rulemaking

proceedings that this clear-as-day prohibition of field burning

does not resolve the meaning of the SIP as it existed as of the

2005 proceedings. Instead, the agency considered Idaho’s “intent” in drafting the SIP, conducting “an examination of the

State’s overall approach to field burning” and “consider[ing]

such things as the legislative history of Idaho’s provisions

related to agricultural burning and smoke management,” various reports and plans prepared by the State, and various

agreements signed by the State. Final SIP, 70 Fed. Reg. at

39,659. EPA also noted that its own past actions “indicate[ ]

that EPA understood agricultural burning to be allowed in

Idaho and that the SIP does not prohibit it.”

4

Id. at 39,660.

EPA did not, however, justify or explain this approach to

interpreting a SIP, and the approach cannot be reconciled with

the role of SIPs in the federal regulatory scheme.5

[3] Interpreting a similar state implementation plan scheme

under the Clean Water Act,6 the Supreme Court held that the

4None of these past actions, however, purported to interpret the relevant

SIP provisions. Thus, there is no agency interpretation to which courts

must afford deference on the determinative question in this case. 

5Nor is there any indication that EPA has previously taken a position on

the proper way to interpret a SIP. Given this vacuum, the case also does

not implicate agency deference considerations on this key conceptual

issue. 

6Under the Clean Water Act, 

6280 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
Clean Water Act “effectively incorporates into federal law

those state-law standards the Agency reasonably determines

to be ‘applicable.’ In such a situation, then, state water quality

standards — promulgated by the States with substantial guidance from the EPA and approved by the Agency — are part

of the federal law of water pollution control.” Arkansas v.

Oklahoma, 503 U.S. 91, 110 (1992) (footnote omitted). Similarly, a SIP, once approved by EPA, has “the force and effect

of federal law.” Trs. for Alaska, 17 F.3d at 1210 n.3 (quoting

Union Elec., 515 F.2d at 211) (internal quotation marks omitted). In accord with this general proposition, a state may not

unilaterally alter the legal commitments of its SIP once EPA

approves the plan. See 42 U.S.C. § 7416 (“[I]f an emission

standard or limitation is in effect under an applicable implementation plan . . . such State or political subdivision may not

adopt or enforce any emission standard or limitation which is

less stringent than the standard or limitation under such plan

. . . .”); Gen. Motors Corp. v. United States, 496 U.S. 530, 540

(1990) (“There can be little or no doubt that the existing SIP

remains the ‘applicable implementation plan’ even after the

State has submitted a proposed revision.”). 

[4] Thus, the SIP became federal law, not state law, once

EPA approved it, and could not be changed unless and until

EPA approved any change. Consequently, the state’s interpretation of the regulations incorporated into the SIP, even if

binding as a matter of state law, is not directly dispositive of

the meaning of the SIP. 

“water quality standards” are, in general, promulgated by the

States and establish the desired condition of a waterway. . . .

[T]he Act requires, inter alia, that state authorities periodically

review water quality standards and secure the EPA’s approval of

any revisions in the standards. If the EPA recommends changes

to the standards and the State fails to comply with that recommendation, the Act authorizes the EPA to promulgate water quality standards for the State. 

Arkansas v. Oklahoma, 503 U.S. 91, 101 (1992) (citing 33 U.S.C. § 1313).

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6281
[5] Accordingly, we look to the standards governing the

interpretation of federal regulations. As a general interpretative principle, “the plain meaning of a regulation governs.”

Wards Cove Packing Corp. v. Nat’l Marine Fisheries Serv.,

307 F.3d 1214, 1219 (9th Cir. 2002). Other interpretative

materials, such as the agency’s own interpretation of the regulation, should not be considered when the regulation has a

plain meaning. See id. (citing Christensen v. Harris County,

529 U.S. 576, 588 (2000)); see also Roberto v. Dep’t of the

Navy, 440 F.3d 1341, 1350 (Fed. Cir. 2006) (“If the regulatory language is clear and unambiguous, the inquiry ends with

the plain meaning.”). 

[6] The plain language of a regulation, however, will not

control if “clearly expressed [administrative] intent is to the

contrary or [if] such plain meaning would lead to absurd

results.” Dyer v. United States, 832 F.2d 1062, 1066 (9th Cir.

1987).7 Although “clearly expressed . . . intent” of regulators

therefore could overcome the plain meaning of a regulation,

see id., we have never considered how definitely and in what

form such intent must be expressed. Doing so now, we conclude that the notice requirements of the APA, 5 U.S.C.

§§ 552(a)(1), 553(b),8 requires that some indication of the reg7Dyer uses the term “legislative intent,” but then inquires into the intent

of the promulgating executive agency, not that of Congress. 832 F.2d at

1066. That focus makes sense, so, for clarity, we use “administrative

intent.” 

8As pertinent here, these requirements provide: 

Each agency shall separately state and currently publish in the

Federal Register for the guidance of the public — 

. . . 

(D) substantive rules of general applicability adopted as

authorized by law, and statements of general policy or interpretations of general applicability formulated and adopted by

the agency; and 

(E) each amendment, revision, or repeal of the foregoing. 

6282 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
ulatory intent that overcomes plain language must be referenced in the published notices that accompanied the

rulemaking process. Otherwise, interested parties would not

have the meaningful opportunity to comment on proposed

regulations that the APA contemplates, id. § 553(c),9 because

Except to the extent that a person has actual and timely notice of

the terms thereof, a person may not in any manner be required to

resort to, or be adversely affected by, a matter required to be published in the Federal Register and not so published. For the purpose of this paragraph, matter reasonably available to the class of

persons affected thereby is deemed published in the Federal Register when incorporated by reference therein with the approval of

the Director of the Federal Register. 

5 U.S.C. § 552(a)(1). 

General notice of proposed rule making shall be published in the

Federal Register, unless persons subject thereto are named and

either personally served or otherwise have actual notice thereof

in accordance with law. The notice shall include — 

(1) a statement of the time, place, and nature of public rule

making proceedings; 

(2) reference to the legal authority under which the rule is

proposed; and 

(3) either the terms or substance of the proposed rule or a

description of the subjects and issues involved. . . . 

Id. § 553(b). 

9That provision mandates: 

After notice required by this section, the agency shall give interested persons an opportunity to participate in the rule making

through submission of written data, views, or arguments with or

without opportunity for oral presentation. After consideration of

the relevant matter presented, the agency shall incorporate in the

rules adopted a concise general statement of their basis and purpose. When rules are required by statute to be made on the record

after opportunity for an agency hearing, sections 556 and 557 of

this title apply instead of this subsection. 

5 U.S.C. § 553(c). This opportunity for comment applies to SIP revisions.

Ober v. U.S. EPA, 84 F.3d 304, 312 (9th Cir. 1996). 

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6283
they would have had no way of knowing what was actually

proposed. For, as the D.C. Circuit has observed:

Courts’ reliance on the “plain meaning” rule in

this setting [of interpreting administrative regulations] is not a product of some fetishistic attraction

to legal “formalism.” In order to infuse a measure of

public accountability into administrative practices,

the APA mandates that agencies provide interested

parties notice and an opportunity for comment

before promulgating rules of general applicability.

This right to participate in the rulemaking process

can be meaningfully exercised, however, only if the

public can understand proposed rules as meaning

what they appear to say. Moreover, if permitted to

adopt unforeseen interpretations, agencies could constructively amend their regulations while evading

their duty to engage in notice and comment procedures. As applied to agency regulations, then, the

plain meaning doctrine is an interpretive norm essential to perfecting the scheme of administrative governance established by the APA. 

. . . . 

. . . To protect the integrity of [the APA’s

required] procedures, we cannot permit an agency to

rely on its unexpressed intentions to trump the ordinary import of its regulatory language. 

Exportal Ltda. v. United States, 902 F.2d 45, 50-51 (D.C. Cir.

1990) (citations and emphases omitted). 

Such a mode of interpretation is particularly sensible under

the CAA, which requires that judicial challenges be filed

within sixty days of a SIP’s approval. 42 U.S.C. § 7607(b)(1).

If an agency can promulgate a regulation with plain language

that dictates one meaning but later interpret it according to an

6284 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
intent indicated neither in the regulatory language nor in the

promulgation documents, parties may depend on the plain

meaning of the regulation in deciding not to launch a challenge within the prescribed time limit. If, later, the agency

relies on an undisclosed intended meaning, interested parties

might be foreclosed from challenging the regulation, contrary

to the statutory permission to launch such challenges.10

[7] Here, following the plain language prohibiting field

burning in Idaho’s 2003 SIP does not produce “absurd

results” or contravene the pertinent administrative history. See

Dyer, 832 F.2d at 1066. As the administrative record of air

quality and health problems created by field burning demonstrates, it is far from patently inconceivable that the federal air

pollution law covering Idaho would ban a significant source

of the state’s particulate pollution. Indeed, one of Idaho’s

neighbors has enacted a broad ban, except in limited circumstances, on the open burning on farms that produce grass seed.

See WASH. ADMIN. CODE 173-430-045 (2006). So the interpretation of the 2003 SIP mandated by its plain language is not

absurd at all, much less sufficiently absurd to justify departure

from a plain words interpretation. See Crooks v. Harrelson,

282 U.S. 55, 60 (1930) (“[T]o justify a departure from the letter of the law upon that ground, the absurdity must be so gross

as to shock the general moral or common sense.”). 

[8] Likewise, no administrative intent expressed in an

appropriate way contradicts the plain meaning of the SIP:

None of the published notices that accompanied the consideration or adoption of Idaho’s previous SIPs established any

intent concerning field burning. Instead, EPA’s purported

intent to allow field burning in Idaho is demonstrated, if at all,

10When review is sought “based solely on grounds arising after such

sixtieth day,” the CAA also allows for the challenge to be “filed within

sixty days after such grounds arise.” 42 U.S.C. § 7607(b). We take no

position on whether EPA’s reliance on its previously undisclosed intent in

approving a SIP could constitute “grounds arising after such sixtieth day.”

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6285
only through informal materials such as letters and presentations and its silent acquiescence when approving certain antipollution strategies submitted by Idaho.11 Although Idaho lawmakers and regulators made their intentions toward field

burning known through more formal actions, such as enacting

legislation and regulations allowing field burning, none of

these measures were referenced in the published materials that

accompanied adoption of the earlier SIPs. 

C.

For the first time on appeal, EPA proffers two additional

reasons we should not rely on the plain meaning of the 2003

and earlier SIPs. We owe no deference to these post hoc litigating positions, adopted by counsel for EPA. See Bowen v.

Georgetown Univ. Hosp., 488 U.S. 204, 212 (1988) (“[W]e

have declined to give deference to an agency counsel’s interpretation of a statute where the agency itself has articulated no

position on the question . . . .”). We do not find EPA’s arguments persuasive. 

EPA argues, first, that giving effect to the plain meaning of

a SIP contrary to the true intent of state policymakers would

violate case law prohibiting EPA from enacting more stringent SIP provisions than those proposed by the state. See Riverside Cement Co. v. Thomas, 843 F.2d 1246, 1247-48 (9th

Cir. 1988) (holding that EPA’s approval of a SIP after removing a proviso submitted by the state was arbitrary and capricious); Bethlehem Steel Corp. v. Gorsuch, 742 F.2d 1028,

1035-36 (7th Cir. 1984) (holding the CAA’s partial approval

provision did not allow EPA to make a SIP stricter); cf. Train,

11EPA cites its approval of an area-specific plan that referenced Idaho’s

field burning statute, see supra note 3, to demonstrate that it understood

prior to 2005 that field burning was not banned in Idaho. Final SIP, 70

Fed. Reg. at 39,660. EPA, however, did not refer to the provisions on field

burning when explaining its decision to approve that strategy. See

Approval and Promulgation of Sandpoint, Idaho, Air Quality Implementation Plan, 67 Fed. Reg. 43,006 (June 26, 2002). 

6286 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
421 U.S. at 79 (“[S]o long as the ultimate effect of a State’s

choice of emission limitations is compliance with the national

standards for ambient air, the State is at liberty to adopt whatever mix of emission limitations it deems best suited to its

particular situation.”); Hall, 273 F.3d at 1153 (“By virtue of

the States’ roles in devising a strategy and adopting an implementation plan, . . . ‘[i]t is to the States that the Act assigns

initial and primary responsibility for deciding what emissions

reductions will be required from which sources.’ ” (alteration

in original) (quoting Whitman v. Am. Trucking Ass’ns, Inc.,

531 U.S. 457, 470 (2001))). Those decisions, however, interpreted the CAA’s provisions concerning the authority of EPA

to approve or deny SIPs. They are not relevant to the task

presently before the court — interpreting SIP language that

was originally proposed by the state. As to that endeavor,

requiring states to express their intent understandably when

submitting proposed SIPs in no way detracts from states’ critical role in devising the strategy to be used in achieving the

requisite air quality standards. 

Second, EPA argues that crediting the SIP’s plain meaning

would contradict case law prohibiting EPA from approving

SIPs based on “an elusive and illusory measure.” Riverside

Cement, 843 F.2d at 1248. In Riverside Cement, EPA

approved a SIP that contained a provision that explicitly

stated its operation was “contingent upon the results of ongoing factfinding.” Id. at 1247 (internal quotation mark omitted). Because that provision, by its own terms, might never

have become effective, the court held EPA could not rely on

that provision in determining whether the SIP met the CAA’s

pollution reduction requirements. Id. at 1248. In this case, by

contrast, nothing on the face of Idaho’s SIP suggests that the

field burning prohibition is in any way contingent or indefinite. The plan is therefore not illusory under our case law.

Moreover, by relying on a SIP’s explicit language to find it

illusory, Riverside Cement supports our broader conclusion

that the plain meaning of a SIP controls. 

SAFE AIR FOR EVERYONE v. UNITED STATES EPA 6287
* * *

[10] In sum, we hold that SIPs are interpreted based on

their plain meaning when such a meaning is apparent, not

absurd, and not contradicted by the manifest intent of EPA, as

expressed in the promulgating documents available to the

public. Because the prohibitory language of the preexisting

Idaho SIP plainly applies to field burning, federal law banned

field burning in Idaho prior to EPA’s 2005 approval of the

SIP amendment. 

III.

In commenting to EPA about Idaho’s proposed amendment

to the SIP, SAFE maintained that its approval would weaken

the prior SIP and thereby violate sections 110(l) and 193 of

the CAA. Section 110(l) provides that EPA “shall not approve

a revision of a [SIP] if the revision would interfere with any

applicable requirement concerning attainment and reasonable

further progress . . . or any other applicable requirement of

this chapter.” 42 U.S.C. § 7410(l). Section 193 provides that

“[n]o control requirement in effect, or required to be adopted

by an order, settlement agreement, or plan in effect before

November 15, 1990, in any area which is a nonattainment

area for any air pollutant may be modified after November 15,

1990, in any manner unless the modification insures equivalent or greater emission reductions of such air pollutant.” Id.

§ 7515. In its 2005 approval of the amendment, EPA denied

the amendment contravened either of these statutes. Final SIP,

70 Fed. Reg. at 39,659-60. SAFE now challenges those determinations. We do not reach those broad statutory challenges,

except to hold that EPA’s reasoning in rejecting them cannot

be squared with our interpretation of Idaho’s pre-2005 SIPs.

As we have explained, EPA’s decision to approve the 2005

amendment to Idaho’s SIP rested on the fundamental premise

that “EPA does not believe that Idaho’s existing SIP when

viewed in its entirety prohibits the burning of crop residue.”

6288 SAFE AIR FOR EVERYONE v. UNITED STATES EPA
Id. at 39,659 (emphasis added). EPA relied on this premise in

rejecting SAFE’s claims under sections 110(l) and 193. See

id. at 39,660 (“The proposed SIP revision is merely a clarification of the existing SIP and does not change or otherwise

relax an existing control measure and therefore will not interfere with any applicable requirements concerning attainment

and reasonable further progress or other applicable requirement of the Act. EPA believes that the requirement of section

110(l) is satisfied.” (emphasis added)); id. (“In sum, EPA

believes that approving the proposed SIP revision does not

change or alter the existing SIP in Idaho which does not prohibit burning of crop residue. . . . Therefore, the requirements

of section 193 of the Act are satisfied.” (emphasis added)).

Moreover, EPA has continued to rely on the same logic in its

brief to this court: “In approving [the 2005] amendment to

Idaho’s SIP, EPA understood it to be a clarification of existing state law and the SIP, governing open burning of crop residue. EPA’s action to approve Idaho’s SIP revision request

therefore did not relax Idaho’s pre-existing SIP with respect

to open burning of crop residue, or any control requirements

in the SIP that had been in effect before November 15, 1990.”

(Emphases added). 

We must review the EPA’s actions based on the “grounds

. . . upon which the record discloses that its action was based.”

Chenery, 318 U.S. at 87; see also Ctr. for Biological Diversity, 466 F.3d at 1103-04. On one hand, that principle means

that we can only uphold EPA’s action “on the basis articulated by the agency itself.” Motor Vehicle Mfrs. Ass’n of the

U.S., Inc. v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 50

(1983). On the other hand, it also means we must “remand to

the agency for additional investigation or explanation” when

the agency’s analysis is incomplete after its flawed basis is

removed. INS v. Ventura, 537 U.S. 12, 16 (2002) (per curiam)

(quoting Fla. Power & Light Co. v. Lorion, 470 U.S. 729, 744

(1985) (internal quotation mark omitted)). The record demonstrates that because EPA based the action under review on its

belief that the preexisting SIP did not ban agricultural burnSAFE AIR FOR EVERYONE v. UNITED STATES EPA 6289
ing, the agency did not address the question whether the 2005

amendment, if indeed a change, contravened the statutory

requirements. We therefore cannot reach that question either.

[11] We have held EPA’s conclusion that the preexisting

SIP did not ban field burning legally erroneous. Because that

flawed premise is fundamental to EPA’s determination that it

did not contravene sections 110(l) or 193 of the CAA by

approving the 2005 SIP, EPA’s outcome on those statutory

interpretation questions is “arbitrary, capricious, or otherwise

not in accordance with law” for the purposes of our review.

Hall, 273 F.3d at 1155. We therefore grant SAFE’s petition,

vacate EPA’s approval of the amendment, and remand to EPA

for its consideration of Idaho’s proposed amendment as a

change in the preexisting SIP, rather than as simply a “clarification” of it. Final SIP, 70 Fed. Reg. at 39,660. Accordingly,

we have no reason to interpret the meaning of either CAA

provision relied upon by SAFE but will instead allow EPA the

first opportunity to apply those provisions, this time in accord

with the understanding that the preexisting SIP bans field

burning while the proposed amendment clearly allows, and

regulates, the practice. 

Petition for Review GRANTED; EPA’s approval

VACATED; REMANDED to EPA.

6290 SAFE AIR FOR EVERYONE v. UNITED STATES EPA