Supreme Court justices were skeptical yesterday about a federal law that allows women who have been sexually assaulted to sue their attackers for money damages. The justices suggested by their remarks that a key provision of the 1994 Violence Against Women Act may ultimately be declared unconstitutional.

In an hour of rapid-fire questions and sometimes testy exchanges, several justices expressed concerns that if Congress were allowed to regulate rapes and local sexual assaults, it would be able to control other traditional areas of state legal systems.

"Your approach," Justice Sandra Day O'Connor told Solicitor General Seth P. Waxman, "would justify a federal remedy for alimony or child support."

Justice Antonin Scalia warned that "the entire realm of criminal law" might be co-opted by the federal government. Justice Anthony M. Kennedy similarly worried that the federal government could, under the Justice Department's theory, assert control over murder and robbery.

The stakes in this case are high, for individual victims and the people they sue, as well as for the nation's constitutional structure and division of powers between the states and the federal government.

The law allowing federal penalties for rapists and other perpetrators of violence against women was several years in the making, as Congress responded to what it called "a national tragedy played out every day in the lives of millions of American women." Yesterday's test case was brought by Christy Brzonkala, a former Virginia Polytechnic Institute student who alleges she was raped in 1994 by two football players, Antonio J. Morrison and James L. Crawford. "Rape is like having your soul torn out," she told reporters last week. "We will never have equal rights in this country until we address violence against women."

But the U.S. Court of Appeals for the 4th Circuit ruled that the federal law is not the way to do it. In a decision last year taking a narrow view of federal power, it struck down the provision allowing for private federal lawsuits as beyond congressional authority. It rejected arguments that the law flowed from Congress's power to regulate interstate commerce and to enforce civil rights--in this case, to take care of victims of "gender-motivated violence" and ensure equal protection of the laws.

Representing Brzonkala yesterday, lawyer Julie Goldscheid told the justices that Congress was rightly addressing "one of the most persistent barriers to women's equality and full participation in the economy."

Separately, Waxman emphasized that Congress was specifically responding to archaic prejudices and sex stereotypes among police, prosecutors and judges in the states, elements that generally wouldn't arise outside the sex crimes area.

Representing the men accused of raping Brzonkala, lawyer Michael E. Rosman told the court that the Justice Department's theory was unconstitutionally broad and would justify any federal legislation aimed at state crimes. The two men were never prosecuted under state law.

Justice Ruth Bader Ginsburg challenged Rosman to explain why Congress couldn't join with the states in addressing violence against women, providing alternative remedies and complementing state efforts. Ginsburg observed that in an earlier era the federal government and states had passed harmonious laws against race discrimination in hotels and other public places.

"But this isn't commerce," Rosman said. "This is violence. This is interpersonal violence" that he characterized as under states' purview. A ruling in the case of United States v. Morrison is likely before summer, when the court recesses.