The Supreme Court, giving police and other public officials more leeway to act without fear of being sued, ruled yesterday that law enforcement officers who conduct illegal searches are immune from liability if they reasonably believed that their actions were constitutional.

The 6-to-3 decision, written by Justice Antonin Scalia, came in a lawsuit brought by a Minnesota couple against an FBI agent who, without obtaining a warrant, unsuccessfully searched their home for a relative suspected of bank robbery. The couple claimed that the Federal Bureau of Investigation and police invaded their St. Paul home on the night of Nov. 11, 1983, brandishing guns, terrorizing their three young daughters and remarking, "You watch too much TV," when asked whether they had a search warrant.

Even if the general rule is "clearly established" that police must obtain search warrants for homes under most circumstances, Scalia said, the agent is entitled to try to prove that he could "reasonably have believed that the search . . .was lawful."

The ruling sparked a vigorous dissent by Justice John Paul Stevens, who accused the majority of "stunningly restrict{ing} the constitutional accountability of police" and "displaying remarkably little fidelity" to the concerns for "the privacy interest of innocent citizens" enshrined in the Fourth Amendment guarantee against unreasonable searches.

But Solicitor General Charles Fried praised the court for making "law enforcement officials generally acting in a reasonable way and in good faith much more secure in their protection against harassing lawsuits."

However, David Rudovsky, who wrote a friend-of-the-court brief on behalf of the Minnesota couple for the American Civil Liberties Union, said the decision will "make constitutional rights even more difficult to enforce," shielding police from suits even in situations where it was clear that they needed a warrant.

In other decisions yesterday, the court, ruling 6 to 3, upheld a 1984 federal law requiring welfare recipients to count child-support payments as part of household income, a cost-saving measure projected to save $455 million during its first three years.

Splitting 5 to 4, the justices also ruled that the U.S. Olympic Committee has the right to prevent a homosexual group from describing its athletic competitions as the "Gay Olympic Games."

The immunity case, Anderson v. Creighton, overturned a decision by the Eighth Circuit U.S. Court of Appeals in St. Louis, which found that FBI agent Russell Anderson had no immunity from suit because it had been "clearly established" that individuals have a constitutional right to be free from warrantless searches of their homes unless officers have probable cause to search and "exigent circumstances" prevent them from obtaining a warrant.

"It simply does not follow from the conclusion that it was firmly established that warrantless searches not supported by probable cause and exigent circumstances violate the Fourth Amendment, that Anderson's search was objectively legally unreasonable," Scalia said.

"We have recognized that it is inevitable that law enforcement officials will in some cases reasonably but mistakenly conclude that probable cause is present, and we have indicated that in such cases those officials -- like other officials who act in ways they reasonably believe to be lawful -- should not be held personally liable," he added. "The same is true of their conclusions regarding exigent circumstances."

The court ordered the case sent back to the lower courts to determine "whether the actions the {couple} allege Anderson to have taken Yesterday's Supreme Court decision will "make constitutional rights even more difficult to enforce."

-- ACLU attorney David Rudovsky

are actions that a reasonable officer could have believed lawful."

Stevens, joined in his dissent by Justices William J. Brennan Jr. and Thurgood Marshall, lambasted the majority for inventing "a new rule of law that protects federal agents who make forcible nighttime entries into the homes of innocent citizens without probable cause, without a warrant and without any valid emergency justification for their warrantless search."

The decision, Stevens warned, "allows federal agents to ignore the limitations of the probable-cause and warrant requirements with impunity." The court, he said, "seems prepared and even anxious in this case to remove any requirement that the officer must obey the Fourth Amendment when entering a private home."

The case arose after a bank robbery in which police suspected Vadaain Dixon, a convicted armed robber on furlough from a halfway house. After failing to find Dixon at two other homes, officers arrived at the home of his sister, Sarisse Creighton, five hours after the robbery and demanded to conduct a search.

Creighton claimed that one of the officers pointed a shotgun at her and that the police yelled at her daughters to "sit their damn asses down and stop screaming." Creighton and her husband, Robert, alleged that officers punched Robert Creighton -- the officer claimed that Robert Creighton tried to grab his shotgun -- and then hit their 10-year-old daughter as she screamed for help.

"This is a totally innocent person who had his Fourth Amendment rights violated," said ACLU lawyer Rudovsky.

The welfare case, Bowen v. Gilliard, involves a 1984 law that changed the Aid to Families with Dependent Children program to require that all children who live in the same home be included in determining families' eligibility for benefits and that welfare payments be reduced by roughly the amount of child support received.

Stevens said the law is justified by the government's "interest in distributing benefits among competing needy families in a fair way." He said Congress acted rationally in seeking "to identify a group that would suffer less than others as a result of a reduction in benefits."

But Brennan and Marshall said that the law impermissibly infringes on childrens' fundamental interest in maintaining relationships with both their parents.

"The government has decreed that the only way a child can live with its mother and be supported by its father is if the mother is wealthy enough not to require public assistance . . . ," Brennan said. "No society can assure its children that there will be no unhappy families. It can tell them, however, that their government will not be allowed to contribute to the pain."

Justice Harry A. Blackmun dissented separately.

In the Gay Olympics case, San Francisco Arts & Athletics Inc. v. U.S. Olympic Committee, Justice Lewis F. Powell Jr. said Congress had the right to grant the Olympic Committee the exclusive right to use the word "olympic."

He dismissed a claim that "olympic" is a generic word that cannot constitutionally be given trademark protection and that the First Amendment bars such protection.

Powell also said the U.S. Olympic Committee could not be sued for allegedly discriminating against the gay group in denying it the right to use "olympic."

Justices Sandra Day O'Connor and Blackmun dissented on the ground that the Olympic Committee was subject to suit. Brennan and Marshall dissented on that ground and also said the statute granting the Olympic Committee the exclusive right to use the word unconstitutionally infringes on free speech.

In another decision yesterday, the court made it easier for women to win child support from men who deny paternity. Justice John Paul Stevens, writing the 8-to-1 decision in Rivera v. Minnich, said mothers need only show it is "more likely than not" that their claim is true and do not need to prove paternity by "clear and convincing evidence."

Justice Brennan dissented.