When a court reviews an agencys 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, 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, 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 agencys 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. If Congress has explicitly left a gap for the agency to fill, there is an express delegation 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. 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 provision for a reasonable interpretation made by the administrator of an agency.

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

Based on the examination of the legislation and its history which follows, we conclude that the EPAs use of that concept here is a reasonable policy choice for the agency to make.

The judgment of the Court of Appeals is reversed.

Question for Analysis

Congress did not specify that the EPA could use a bubble in measuring pollution emitted from an industrial facility, so why could the EPA come up with such a rule?