“ The Section uses the words 'any Act of Congress.' As against petitioners' contention that all legislation passed by Congress is embraced within that language, it is urged that a proper interpretation of Section 2282 confines the phrase 'Act of Congress' to laws having general application throughout the United States. ”

“ One of the jurisdictional questions raised by this case is whether a court of three judges is required by Section 2282 in a suit to enjoin enforcement of congressional enactments affecting only the District of Columbia. ”