THE BALANCE of power between the federal government and the states -- the subject that preoccupied the Supreme Court this week -- is one of the enduring tensions in the structure of American government. In recent decades, liberals have tended to be enthusiastic about the use of federal power, especially to protect the rights of minorities and the interests of the poor. Conservatives have urged invigoration of the states as a way of limiting the reach of the federal government. But the debate about how to strike the constitutional balance shouldn't break down along political lines. The proper question is whether the justices are letting policy issues be addressed by the appropriate level of government, rather than which level is likely to deliver a particular favored outcome.

The court does a service, not to mention its duty, in sorting through these issues. But its recent work -- including that of the past few days -- has been uneven. Some of it, such as the continuing effort to define the scope of Congress's power to regulate interstate commerce, is healthy. Some, such as its unanimous decision the other day to uphold a federal privacy protection that restricts states' dissemination of information from drivers' license applications, is deferential to Congress. But some, such as the decision Tuesday to strengthen the already aggrandized doctrine of state sovereign immunity, seems a naked exercise in conservative judicial activism.

On the healthy side, the court heard arguments Tuesday in a case concerning a federal 1994 law giving victims of gender-motivated violence the right to sue their attackers in federal court. The government contends that the Violence Against Women Act is a legitimate exercise of Congress's power under the commerce clause of the Constitution, because Congress found that violence against women has a significant effect on commerce -- particularly by impeding women's travel and employment. If this is right, it is hard to imagine any area of life from which Congress would be precluded from legislating. The plaintiff in this case -- a woman who alleges she was raped in a college dormitory by two football players -- is a very sympathetic figure, but Congress can't use the pretext of the commerce clause to right every wrong.

The court should strike down this law, but carefully, so as not to restrict Congress from legislating in areas, such as environmental protection, where congressional acts affect commercial and noncommercial activities alike. How the court draws this line is all-important, but its insistence that Congress consider the boundaries of its commerce clause power is valuable.

Far less valuable is the court's perverse holding Tuesday in Kimel v. Florida Board of Regents. A 5 to 4 majority held that a federal age-discrimination law could not constitutionally authorize suits by state workers against the state entities that employ them. This is the latest in a string of wrongheaded decisions that have made a kind of fetish out of state sovereign immunity. This doctrine, which holds that state governments can't be sued for damages, does not actually appear in the Constitution. The court has essentially created the doctrine and then used it to allow state governments to deprive their employees of federally granted protections that all other Americans enjoy.

The Kimel case is particularly upsetting, as it extends this broad reading of state sovereign immunity into the area of anti-discrimination, where the historical and constitutional justifications for robust congressional powers are especially strong. The real-world repercussions of Kimel will probably be muted, since it affects only state employees, and states offer anti-discrimination protections in their own courts. But this line of cases takes too expansive a view of what the fact of statehood really means.