mit program-its "raison d'être," in the court's view-was to improve air quality, the court held that the bubble concept was inapplicable in these cases under its prior precedents. Ibid. It therefore set aside the regulations embodying the bubble concept as contrary to law. We granted certiorari to review that judgment, 461 U. S. 956 (1983), and we now

reverse.

The basic legal error of the Court of Appeals was to adopt a static judicial definition of the term "stationary source" when it had decided that Congress itself had not commanded that definition. Respondents do not defend the legal reasoning of the Court of Appeals. Nevertheless, since this Court reviews judgments, not opinions, we must determine whether the Court of Appeals' legal error resulted in an erroneous judgment on the validity of the regulations.

II

8

When a court reviews an agency's construction of the statute which it administers, it is confronted with two questions. First, always, is the question 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,

'Respondents argued below that EPA's plantwide definition of "stationary source" is contrary to the terms, legislative history, and purposes of the amended Clear Air Act. The court below rejected respondents' arguments based on the language and legislative history of the Act. It did agree with respondents contention that the regulations were inconsistent with the purposes of the Act, but did not adopt the construction of the statute advanced by respondents here. Respondents rely on the arguments rejected by the Court of Appeals in support of the judgment, and may rely on any ground that finds support in the record. See Ryerson v. United States, 312 U. S. 405, 408 (1941); LeTulle v. Scofield, 308 U. S. 415, 421 (1940); Langnes v. Green, 282 U. S. 531, 533–539 (1931).

8

E. g., Black v. Cutter Laboratories, 351 U. S. 292, 297 (1956); J. E. Riley Investment Co. v. Commissioner, 311 U. S. 55, 59 (1940); Williams v. Norris, 12 Wheat. 117, 120 (1827); McClung v. Silliman, 6 Wheat. 598, 603 (1821).

as well as the agency, must give effect to the unambiguously expressed intent of Congress." If, however, the court determines Congress has not directly addressed the precise question at issue, the court does not simply impose its own construction on the statute,10 as would be necessary in the absence of an administrative interpretation. Rather, if 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." "The power of an administrative agency to administer a congressionally created. . . program necessarily requires the formulation of policy and the making of rules to fill any gap left, implicitly or explicitly, by Congress." Morton v. Ruiz, 415 U. S. 199, 231 (1974). If Congress has explicitly left a gap for the agency to fill, there is an express delegation

9

The judiciary is the final authority on issues of statutory construction and must reject administrative constructions which are contrary to clear congressional intent. See, e. g., FEC v. Democratic Senatorial Campaign Committee, 454 U. S. 27, 32 (1981); SEC v. Sloan, 436 U. S. 103, 117-118 (1978); FMC v. Seatrain Lines, Inc., 411 U. S. 726, 745-746 (1973); Volkswagenwerk v. FMC, 390 U. S. 261, 272 (1968); NLRB v. Brown, 380 U. S. 278, 291 (1965); FTC v. Colgate-Palmolive Co., 380 U. S. 374, 385 (1965); Social Security Board v. Nierotko, 327 U. S. 358, 369 (1946); Burnet v. Chicago Portrait Co., 285 U. S. 1, 16 (1932); Webster v. Luther, 163 U. S. 331, 342 (1896). If a court, employing traditional tools of statutory construction, ascertains that Congress had an intention on the precise question at issue, that intention is the law and must be given effect.

10 See generally, R. Pound, The Spirit of the Common Law 174-175 (1921).

"The court need not conclude that the agency construction was the only one it permissibly could have adopted to uphold the construction, or even the reading the court would have reached if the question initially had arisen in a judicial proceeding. FEC v. Democratic Senatorial Campaign Committee, 454 U. S., at 39; Zenith Radio Corp. v. United States, 437 U. S. 443, 450 (1978); Train v. Natural Resources Defense Council, Inc., 421 U. S. 60, 75 (1975); Udall v. Tallman, 380 U. S. 1, 16 (1965); Unemployment Compensation Comm'n v. Aragon, 329 U. S. 143, 153 (1946); McLaren v. Fleischer, 256 U. S. 477, 480-481 (1921).

of authority to the agency to elucidate a specific provision of the statute by regulation. Such legislative regulations are given controlling weight unless they are arbitrary, capricious, or manifestly contrary to the statute. 12 Sometimes the legislative delegation to an agency on a particular question is implicit rather than explicit. In such a case, a court may not substitute its own construction of a statutory provison for a reasonable interpretation made by the administrator of an agency. 13

We have long recognized that considerable weight should be accorded to an executive department's construction of a statutory scheme it is entrusted to administer," and the principle of deference to administrative interpretations

"has been consistently followed by this Court whenever decision as to the meaning or reach of a statute has involved reconciling conflicting policies, and a full understanding of the force of the statutory policy in the given situation has depended upon more than ordinary knowledge respecting the matters subjected to agency regulations. See, e. g., National Broadcasting Co. v. United States, 319 U. S. 190; Labor Board v. Hearst Publications, Inc., 322 U. S. 111; Republic Aviation Corp. v.

12 See, e. g., United States v. Morton, ante, at 834; Schweiker v. Gray Panthers, 453 U. S. 34, 44 (1981); Batterton v. Francis, 432 U. S. 416, 424-426 (1977); American Telephone & Telegraph Co. v. United States, 299 U. S. 232, 235-237 (1936).

13 E. g., INS v. Jong Ha Wang, 450 U. S. 139, 144 (1981); Train v. Natural Resources Defense Council, Inc., 421 U. S., at 87.

14 Aluminum Co. of America v. Central Lincoln Peoples' Util. Dist., ante, at 389; Blum v. Bacon, 457 U. S. 132, 141 (1982); Union Electric Co. v. EPA, 427 U. S. 246, 256 (1976); Investment Company Institute v. Camp, 401 U. S. 617, 626-627 (1971); Unemployment Compensation Comm'n v. Aragon, 329 U. S., at 153-154; NLRB v. Hearst Publications, Inc., 322 U. S. 111, 131 (1944); McLaren v. Fleischer, 256 U. S., at 480-481; Webster v. Luther, 163 U. S., at 342; Brown v. United States, 113 U. S. 568, 570-571 (1885); United States v. Moore, 95 U. S. 760, 763 (1878); Edwards' Lessee v. Darby, 12 Wheat. 206, 210 (1827).

Labor Board, 324 U. S. 793; Securities & Exchange Comm'n v. Chenery Corp., 332 U. S. 194; Labor Board v. Seven-Up Bottling Co., 344 U. S. 344.

66

". . . If this choice represents a reasonable accommodation of conflicting policies that were committed to the agency's care by the statute, we should not disturb it unless it appears from the statute or its legislative history that the accommodation is not one that Congress would have sanctioned." United States v. Shimer, 367 U. S. 374, 382, 383 (1961).

Accord, Capital Cities Cable, Inc. v. Crisp, ante, at 699-700.

In light of these well-settled principles it is clear that the Court of Appeals misconceived the nature of its role in reviewing the regulations at issue. Once it determined, after its own examination of the legislation, that Congress did not actually have an intent regarding the applicability of the bubble concept to the permit program, the question before it was not whether in its view the concept is "inappropriate" in the general context of a program designed to improve air quality, but whether the Administrator's view that it is appropriate in the context of this particular program is a reasonable one. Based on the examination of the legislation and its history which follows, we agree with the Court of Appeals that Congress did not have a specific intention on the applicability of the bubble concept in these cases, and conclude that the EPA's use of that concept here is a reasonable policy choice for the agency to make.

III

In the 1950's and the 1960's Congress enacted a series of statutes designed to encourage and to assist the States in curtailing air pollution. See generally Train v. Natural Resources Defense Council, Inc., 421 U. S. 60, 63-64 (1975). The Clean Air Amendments of 1970, Pub. L. 91-604, 84 Stat. 1676, "sharply increased federal authority and responsibility

15

in the continuing effort to combat air pollution," 421 U. S., at 64, but continued to assign "primary responsibility for assuring air quality" to the several States, 84 Stat. 1678. Section 109 of the 1970 Amendments directed the EPA to promulgate National Ambient Air Quality Standards (NAAQS's) 15 and § 110 directed the States to develop plans (SIP's) to implement the standards within specified deadlines. In addition, § 111 provided that major new sources of pollution would be required to conform to technology-based performance standards; the EPA was directed to publish a list of categories of sources of pollution and to establish new source performance standards (NSPS) for each. Section 111(e) prohibited the operation of any new source in violation of a performance standard.

Section 111(a) defined the terms that are to be used in setting and enforcing standards of performance for new stationary sources. It provided:

"For purposes of this section:

"(3) The term 'stationary source' means any building, structure, facility, or installation which emits or may emit any air pollutant." 84 Stat. 1683.

In the 1970 Amendments that definition was not only applicable to the NSPS program required by §111, but also was made applicable to a requirement of §110 that each state implementation plan contain a procedure for reviewing the location of any proposed new source and preventing its construction if it would preclude the attainment or maintenance of national air quality standards. 16

In due course, the EPA promulgated NAAQS's, approved SIP's, and adopted detailed regulations governing NSPS's

15 Primary standards were defined as those whose attainment and maintenance were necessary to protect the public health, and secondary standards were intended to specify a level of air quality that would protect the public welfare.

16 See §§ 110(a)(2)(D) and 110(a)(4).