Editors' Summary: The recent wave of citizen suits to enforce federal pollution control laws has touched off waves of controversy, much of it over the fact that citizen enforcers can sue for civil penalties under the Clean Water Act. Two aspects of the civil penalty cases have provoked debate: whether plaintiffs may sue for penalties for past violations where the defendant is now in compliance with the Act, and whether settlements of citizen enforcement suits may direct that payments may be paid to private institutions for environmental quality work in lieu of penalties. This Article raises a third issue, whether Congress may constitutionally authorize citizens to sue for civil penalties in the first place. The author contends that the separation of powers doctrine, as interpreted by the Supreme Court, precludes Congress from assigning executive functions to anyone outside the Executive Branch. Citizen suits for injunctive relief to abate pollution are not barred, because they vindicate the personal interests of the litigants, but suits for penalties serve only the national interest in law enforcement. They therefore are executive functions that may be delegated only to Executive Branch officials.