The U.S. Supreme Court asked Virginia's high court yesterday to decide how a 1985 state law banning the commercial display of sexually explicit publications would be enforced, saying it lacked enough information on the statute to decide its constitutionality.

In an opinion written by Justice William J. Brennan, the court asked Virginia's Supreme Court to determine whether the statute would ban the display of a substantial number of books and magazines, as booksellers have claimed, or would apply only to a few "borderline" works, as Virginia's attorney general argued.

"We have concluded that we should not attempt to decide the constitutional issues presented without first having the Virginia Supreme Court's interpretation of key provisions of the statute," Brennan wrote.

After the state responds, the case could return to the Supreme Court, which heard arguments last year.

The case, Virginia v. American Booksellers Association Inc., is being watched closely in many other states that have similar laws to keep juveniles from seeing displays of sexually explicit material. Twenty states filed briefs with the Supreme Court in support of Virginia's request to declare the law constitutional.

The disputed law, which is not being enforced while its constitutionality is under challenge, prohibits the display "in a manner whereby juveniles may examine and peruse" sexually explicit material, including publications that although not obscene, could be "harmful to juveniles."

Six of Brennan's colleagues joined in his opinion. Justice John Paul Stevens said he was "in substantial agreement," but dissented on the opinion's wording of a question put to the state's highest court.

"We're extremely pleased," a spokesman for Attorney General Mary Sue Terry said of the court's action. Her office is "hopeful" that the state court will declare "that the intent of the legislature was to limit the perusal of this sort of material by minors, not to ban literature from our bookstores."

"I'm somewhat disappointed the court did not move ahead and hold the statute unconstitutional," said American Booksellers' attorney Michael A. Bamberger. "On the other hand, I think it recognized the breadth of the statute raises substantial First Amendment questions."

Virginia's highest court was asked by the justices to say specifically whether any of the 16 books on a list drawn up by the booksellers would be seen as "harmful to juveniles" under the contested statute. Stevens wanted the Virginia court to state which, if any, of the books were affected by the law.

Booksellers argued the law would require them to remove from open display such books as "Hollywood Wives" by Jackie Collins, "The Facts of Love" by Alex and Jane Comfort, and "Forever" by Judy Blume, an author of books for teen-agers.

In addition, the Virginia court was asked how such decisions "should take into account juveniles' differing ages and level of maturity," and finally, whether a bookseller would comply with the law by continuing to display sexually explicit materials, but stopping juveniles from looking at it when they were seen doing so.

Soon after the law was passed in 1985, a coalition of booksellers and publishers challenged its breadth, saying it would require them to place about one-quarter of their inventories either under the counter or in an "adults only" section of their stores.

A federal judge and the 4th U.S. Circuit Court of Appeals found the statute unconstitutional, saying it would impose a "significant" burden on booksellers.