The Supreme Court ruled yesterday that police officers may be forced to pay damages to people they arrest improperly -- even if they had first obtained an arrest warrant signed by a judge.

Police officers, unlike prosecutors and judges, do not enjoy absolute immunity from lawsuits, and "objectively unreasonable" actions will expose them to liability for damages, Justice Byron R. White wrote for the court.

Jerald R. Vaughn, executive director of the International Association of Chiefs of Police, said he was "disappointed" by the ruling. "It raises more concerns" in the minds of officers about their personal liability and "being second-guessed," Vaughn said.

The ruling involved the predawn arrest of Louisa and James R. Briggs, a prominent Rhode Island couple picked up in a drug sweep after their names surfaced in a wiretap of a suspected drug dealer.

The couple was taken to a police station, booked, held for several hours and released. Local and statewide papers reported that the couple had been arrested on drug possession charges. James Briggs is a real estate developer, former president of the Narragansett Chamber of Commerce, former head of the local heart fund and muscular dystrophy drives and former elected town tax assessor.

No indictment was returned against the couple. They sued the state trooper, Edward Malley, who had sought the arrest warrant based on a telephone conversation tapped by another officer, Joseph Miranda, during a drug investigation. The Briggses each asked $2 million in damages for violations of their civil rights.

A trial judge threw out the case, saying that the magistrate's issuance of a warrant entitled Malley to immunity. The 1st U.S. Circuit Court of Appeals overruled, saying that a warrant does not automatically shield police from lawsuits if it can be shown that officers should have known there was no "probable cause" for an arrest.

That limited immunity, White said, "provides ample protection to all but the plainly incompetent or those who knowingly violate the law." The court rejected arguments from 20 states and from law enforcement groups that a magistrate's issuance of a warrant shielded the officer from liability.

In this case, White said, Malley was acting on the basis of a telephone conversation between an unknown person and Paul Driscoll, who knew the Briggses' daughter and whose phone was tapped. The unknown caller said he had smoked marijuana at a party at the Briggses' home "in front of Jimmy Briggs" and that he, the caller, had "passed it to Louisa."

Based on that information, Malley obtained an arrest warrant for the couple for conspiracy to possess marijuana with intent to deliver.

"The question in this case," White said, "is whether a reasonably well-trained officer . . . would have known that [the call] failed to establish probable cause and that he should not have applied for a warrant." White, upholding the appeals court, sent the case back for a jury to decide that issue.

"It is true that in an ideal system an unreasonable request for a warrant would be harmless," White said, "because no judge would approve it. But ours is not an ideal system, and it is possible that a magistrate, working under docket pressures, will fail to perform as a magistrate should. We find it reasonable to require the officer applying for the warrant to minimize this danger by exercising reasonable professional judgment."

Justice Lewis F. Powell Jr., joined by Justice William H. Rehnquist, dissented. Powell said he agreed that police do not enjoy absolute immunity, but said Malley appeared to have been "reasonably competent" and that a magistrate's issuance of a warrant, "although not conclusive, is entitled to substantial evidentiary weight."