When Congress passes legislation, it frequently directs that one or more federal agencies promulgate regulations both implementing the law and filling in details Congress may have left unaddressed. When agencies promulgate these regulations, it often falls to federal courts to review whether those regulations are based upon an appropriate interpretation of the statutes Congress enacted. Inevitably, the executive and judicial branches of government will sometimes have differing interpretations of the language in these statutes. The U.S. Supreme Court considered this interplay of powers in its decision in Chevron U.S.A. v. Natural Resources Defense Council, 467 U.S. 837 (1984). There, the court announced a two-step framework that courts have since utilized to review an agency's statutory interpretation, an approach commonly called "Chevron deference." This analysis requires courts to first ask whether Congress directly and unambiguously addressed the question at issue. If Congress' intent is unclear because the statute is silent or ambiguous, then "the question for the court is whether the agency's answer is based on a permissible construction of the statute." If so, the court is to defer to the agency's interpretation, even if the court would have independently come to a different conclusion.