When historians look back at the Rehnquist Court, without a doubt they will say that its greatest changes in constitutional law were in the area of federalism. Over the past decade, the Supreme Court has limited the scope of Congress's powers and has greatly expanded the protection of state sovereign immunity. In 1995, for the first time in sixty years, the Supreme Court declared a federal law unconstitutional as exceeding the scope of Congress's Commerce Clause power. For only the second and third times in sixty years - and the first time, the case was expressly overruled - the Court invalidated a federal law for violating the Tenth Amendment. At the same time, the Court has used federalism to enlarge the states' sovereign immunity in federal court for violations of federal statutes. These decisions have spawned hundreds of lower court decisions concerning federalism and have ensured that federalism will be a constant issue before the Supreme Court for years to come.

Virtually all of the decisions protecting federalism were by a 5-4 margin, with the majority comprised of Chief Justice William Rehnquist and Justices Sandra Day O'Connor, Antonin Scalia, Anthony Kennedy, and Clarence Thomas. In the last few years of the Rehnquist Court, however, the federalism revolution waned as the Court consistently ruled in favor of federal power. While the Court did not overrule or undercut its earlier decisions, the pendulum did not swing any further in the direction of the federalism revolution. Strikingly, some of its decisions in favor of federal power - such as Tennessee v. Lane and Central Virginia Community College v. Katz - were 5-4 decisions with Justice O'Connor in the majority. Nevada Department of Human Resources v. Hibbs was a 6-3 decision, with both Chief Justice Rehnquist and Justice O'Connor in the majority...