A divided Supreme Court yesterday upheld an arrest even though it was made under a law that later was found to violate the guarantee in the Constitution against unreasonable searches and seizures.

"Police are charged to enforce laws until and unless they are declared unconstitutional," Chief Justice Warren E. Burger wrote for the 6-to-3 majority.

For the dissenters, Justice William J. Brennan wrote that a legislative body cannot validate unconstitutional means used by police officers to gather evidence.

The case involved a Detroit ordinance empowering a police officer with "reasonable cause to believe that the behavior of an individual warrants further investigation for criminal activity" to "stop and question" the person.

As amended in 1976, the ordinance also makes it unlawful for the suspect "to refuse to identify himself, and to produce verifiable documents or other evidence of such identification."

On a night in September 1976, officers in a patrol car, responding to a radio call, found Gary DeFillippo and a woman in an alley. She was in the process of lowering her slacks.

Asked for identification DeFillippo at first claimed to be a police sergeant, but then changed his story to say that he either worked for or knew a "Sergeant Mash."

The officers arrested him for violating the ordinance and then searched him. In one shirt pocket they found marijuana; in the other they found a tinfoil packet that, at the police station, was found to contain a controlled drug, phencyclidine.

DeFillippo was charged with possession of the drug. At arraignment, he asked a judge to suppress the evidence of possession. The judge refused. But a state appeals tribunal disagreed, holding that the ordinance was unconstitutionally vague and that the arrest and search consequently were both invalid.

The appeals tribunal was reversed with the opinion by Chief Justice Burger. Under the ordinance, he said, the officers acted in good faith. They had abundant "probable cause" to make a nighttime arrest of a man who was in an alley in DeFilli ppo's circumstances and who gave "inconsistent and evasive responses" to requests for identification, he wrote.

"The remaining question," Burger said, is whether the officers lacked probable cause to believe they were not witnessing a violation of the ordinance "simply because" they should have known it to be invalid under the Fourth Amendment.

"The answer is clearly negative," Burger wrote. The conduct seen by the officers "violated a presumptively valid ordinance," he said. "The search which followed was valid because it was incidental to [the] arrest."

Brennan, in the dissenting opinion also signed by Justices Thurgood Marshall and John Paul Stevens, wrote that even if authorized by the ordinance, the arrest - made "purely on suspicion" - and search were unconstitutional.

The majority erred in focusing on the good faith of the officers, Brennan said.Had it focused instead on "the ultimate issue" - whether they had gathered evidence unconstitutionally - invalidation of the arrest and search would have been "inescapable," he said.

And, he wrote if the majority only had "explored, rather than simply assumed," the reasons for the ordinance's unconstitutionality, "it would have been obvious" that there had been an unreasonable search and seizure.

It would have been obvious, Brennan said, because under the Fourth Amendment, individuals accosted by police on the basis merely of reasonable suspicion, rather than probable cause, "have a right not to be searched, a right to remain silent."

These rights plainly are abridged by the ordinance and the conduct it purports to authorize, Brennan said. It "commands that which the Constitution denies the state power to command," he said. Furthermore, he said, it engages in "a sheer piece of legislative legerdermain not to be countenanced" making the constitutionally protected right to refused to reply to police inquiries itself an offense.

In a related ruling, the court held, 9 to 0, that El Paso police violated the Fourth Amendment rights of Zackary C. Brown under a Texas law similar to the Detroit ordinace. They lacked any reasonable suspicion to believe that he was engaged or had engaged in criminal conduct, Burger emphasized in the opinion for the court.

"BREATHALYZER" TESTS

by a 5-to-4 vote, the court upheld a Massachusetts law requiring a suspension of up to 90 days of the license of a driver who refused to take a breath-analysis test upon arrest for operating a motor vehicle while drunk.

All states empower police officers to threaten suspension when a driver suspected of being under the influence of intoxicating liquor refused to take a "breathalyzer" test. But in addition to Massachusetts, only 12 states, not including Maryland or Virginia, do not provide a hearing before suspention under so-called "implied consent" statutes.

A panel of three federal judges held that on its face the Massachusetts law denied the due process of law guaranteed by the Constitution. A hearing should precede suspension, the panel held.

In the opinion reversing the panel, Chief Justic Burger wrote that Donald E. Montrym, a motorist who had challenged the law, "could have obtained an immediate hearing before the registrar [of motor vehicles] at any time after he had surrendered his license."

For the dissenters, however, Justice Potter Stewart termed this remedy "largely fictional" because the state does not notify the driver of its availability and because it is a mere 'walkin' procedure providing "little more than a right to request the scheduling of a later hearing. In the meantime, the license suspension continues . . ." His opinion has signed by Brennan, Marshall and Stevens.