is a principle of political change, spurred by conservative activism, that seeks to limit federal authority and return to the states. It has taken on significant political importance in health care policy with contentious debate over which level of government should set standards, as well as perform and pay for services. Just as important, the Supreme Court has been engaged in a conservative project that fundamentally alters the balance between the supremacy of federal law and the separate sovereignty of the states.[1] Three cases in the Supreme Court's 2000 term symbolize this transformation in American federalism--involving privacy, violence against women, and age discrimination. The legal arguments may not interest those concerned with health policy and ethics, but they should. The Supreme Court has explored the contours of a new federalism in which states retain a sphere of autonomy in matters of public health and safety. A reenergized conservative majority on the Supreme Court, led by Justices Rehnquist and Scalia, has been actively denying Congress the to enact and enforce important public health and civil rights legislation. The Rehnquist Court has implemented its interpretation of a states-rights agenda in two ways: limiting federal and defending state sovereign immunity. National Power to Protect Health and Safety The Supreme Court's 1995 decision in United States v. Lopez[2] signaled a change in the Court's view about the balance of federal and state in the constitutional design. In Lopez, the Court held that Congress exceeded its commerce clause authority by making gun possession within a school zone a federal offense. Concluding that gun violence did not substantially affect interstate commerce, the Court declared the statute unconstitutional. In Printz v. United States,[3] this time using the Tenth Amendment's reserved powers doctrine, the Court overturned provisions in the Brady Handgun Violence Prevention Act that directed state and local law enforcement officers to conduct background checks on prospective handgun purchasers. (The Court has used similar reserved power arguments to overturn federal environmental initiatives.[4]) Here are cases where the nation's highest court was prepared to invalidate politically popular measures thought to be important to the public's health and safety. The Court did not invalidate these laws on grounds that regulating firearms was an unimportant aim of government, but only that it was outside the reach of the federal government. States would still be free to legislate in traditional realms of public health, but Lopez and Printz left little doubt that the Rehnquist Court would henceforth examine the exercise of federal police authority. These cases probably do not indicate a wholesale retreat from national public health that emerged with Franklin Delano Roosevelt's New Deal. Certainly, Congress will continue to have wide authority to regulate businesses and individuals when they engage in explicitly economic or commercial activity. For example, in Reno v. Condon,[5] decided in the current term, the Court upheld a federal law that restricts the states' ability to disclose personal information in drivers licenses. Because drivers' information is an article of commerce, the Court found that its sale or release into the interstate stream of business is sufficient to support congressional regulation. The important question these cases leave open is the constitutionality of public health regulation of intrastate activity, particularly in the field of environmental protection. Many astute observers predict that during its current term, in United States v. Morrison, the Supreme Court will strike down the Violence Against Women Act as an unconstitutional exercise of the commerce power. The act creates a civil rights remedy, permitting survivors to bring federal lawsuits against perpetrators of sexually motivated crimes of violence. …