THE CASE of Condon v. Reno, which was argued before the Supreme Court last week, pits useful privacy protections against legitimate concerns about states' rights. The case may well prove a vehicle for the high court to continue its restructuring of the relationship between the federal government and the states -- a restructuring that has been, to date, wholly at the expense of congressional powers. The message for Congress: Lawmakers must consider federalism problems before legislating, or the court will do it for them afterward.

The Driver's Privacy Protection Act (DPPA) was passed in 1994 -- before the latest wave of federalism cases -- in response to the commercial sale by states of information given to departments of motor vehicles by applicants for driver's licenses. The concern was that stalkers had used personal information from the departments to find people with unlisted phone numbers and addresses. The DPPA forbade states from making such information available without providing individuals the option of having their information protected. Media organizations, including The Post, use such databases routinely, and the newspaper industry opposed the law. But it is hard to object to the principle that personal information that one is essentially compelled to produce should not be sold without the individual's consent; we have supported privacy restrictions for license information at the state level.

Far less clear is why such a rule should be imposed nationally, rather than letting states carve out their own privacy regimes. Moreover, Congress did not create its rule in the most constitutionally bulletproof fashion. Rather than simply conditioning federal transportation funds on the adoption of privacy provisions, which would have been much more clearly constitutional, the DPPA dictates to the states how and under what circumstances private information can be disclosed. The question is whether this is an improper invasion of state sovereignty. It is a very close call, one over which four courts of appeals have split.

It may be too much to ask that Congress would have anticipated the direction the court would take on federalism questions. And Congress has recently moved to tie federal money to state compliance with the DPPA's provisions -- effectively shoring up the law's foundations. But in an era in which the courts are aggressively probing the limits of legislative powers, it does not seem unreasonable to expect Congress to craft bills in the least constitutionally provocative fashion, and to do so the first time around.