The Supreme Court under Chief Justice Rehnquist’s recent leadership has invalidated numerous federal laws, arguably departing from settled precedent to do so. The Rehnquist Court has held that Congress exceeded its constitutional authority in five instances during the 2000-01 Term, on four occasions during the 1999-2000 Term and in a total of twenty-nine cases since the 1994-95 Term. Commentators typically explain these decisions in federalism terms, focusing on the Court’s use of its power to protect the States from an overreaching Congress. That explanation is incomplete and, in important respects, unpersuasive. The Rehnquist Court has not been as solicitous of states’ rights as one might expect if it were operating primarily from a federalism perspective. Even apart from its highly controversial foray into Florida election law, the Court in recent years has not been shy about invalidating state statutes or governmental actions based on its own conception of what federal power or federal limits require. Moreover, while it is true that many federal laws invalidated since 1995 have involved assertedly unjustified intrusions on state interests, one cannot adequately understand this recent judicial activism toward Congress without employing a separation of powers perspective.