WASHINGTON — In a ruling that cast doubt on the constitutionality of the nation's "hate crime" laws, the Supreme Court on Monday struck down a St. Paul, Minn., ordinance that punishes those who burn crosses, display swastikas or otherwise express religious and racial hatred.

The high court--in a decision reminiscent of its 1989 ruling that knocked down laws prohibiting the burning of an American flag--used the case of a 17-year-old skinhead to issue a sweeping defense of the right to free expression.

The government cannot punish those who "communicate messages of racial, gender or religious intolerance" simply because such ideas are offensive to most and deeply hurtful to some, the court said.

The First Amendment forbids "silencing speech on the basis of its content," wrote Justice Antonin Scalia.

The broad wording of his opinion would appear to invalidate all manner of laws enacted to punish expressions of bigotry and racial hatred.

In recent years, 46 states, including California, have put into effect measures that make it a crime to burn crosses, display Nazi emblems or otherwise convey bias and hatred. Some 200 colleges and universities have followed suit with codes of conduct that discipline those whose words or actions convey racist, sexist or religious intolerance.

The "hate speech" issue has prompted anguished debate among civil libertarians and advocates of rights for blacks, women and other minorities. While some have applauded such laws as protecting victims of bias, others have criticized them for enforcing a new "political correctness" on controversial topics.

Scalia's opinion, speaking for the most conservative members of the court, seems to side with the critics.

As a practical matter, however, the court left officials with ample authority to attack most hate crimes.

For example, the juvenile who burned a cross in the front yard of a black family's home in St. Paul could be charged with arson, trespass or criminal damage to property, the court said. Similarly, the anti-Semite who paints a swastika on a school wall can be punished for defacing public property.

But they cannot be punished simply for expressing a loathsome message, the court said.

"Let there be no mistake about our belief that burning a cross in someone's yard is reprehensible. But St. Paul has sufficient means at its disposal to prevent such behavior without adding the First Amendment to the fire," Scalia said.