Last week three Supreme Court justices -- Byron R. White, John Paul Stevens and Sandra Day O'Connor -- attended a Kennedy Center performance of the New York City Ballet with their spouses as the guests of NYNEX, the telecommunications firm.

The ballet was preceded by a reception at which "heavy hors d'oeuvres" were served, according to one of the hosts -- a typical night on the town in the nation's capital.

But 10 days before, the Supreme Court had rejected an appeal by a subsidiary of NYNEX, the New York Telephone Co., over whether the utility could bill consumers for the costs of its charitable contributions -- a reminder that the sponsors of Washington social events often turn up in public policy disputes of all kinds.

The three justices' acceptance of $45 ballet tickets and attendance at the reception beforehand could be interpreted as a violation of the American Bar Association's Code of Judicial Conduct. A section of the code says that judges should not accept gifts or favors from someone "whose interests have come or are likely to come" before them.

White, the only justice who would comment on the event, said that "big companies are constantly participating in sponsoring events" at the National Gallery or the Smithsonian. "I had not at least until now thought there was any problem about it . . . . I still don't."

Stevens declined to discuss the invitation but his office said he was a guest of NYNEX and that he had not been aware that a petition from a NYNEX affiliate had been among the more than 1,000 petitions reviewed by the court before the term opened Oct. 5.

O'Connor, through Supreme Court press officer Toni House, said she did not know NYNEX had been a litigant before the court.

Richard Adler, a NYNEX spokesman in Washington, said the firm donated $175,000 to underwrite the ballet's trip to Washington. He said it was clear that NYNEX was the major sponsor and invitations were from "NYNEX and the New York congressional delegation."

"There is no implied reciprocity," he said. "It was just an enjoyable evening . . . for people who enjoy the ballet. It was a social event."

Adler said a broad range of well-known Washington figures were invited -- members of the congressional committees that oversee telecommunications issues; ambassadors, business leaders, the eight Supreme Court justices and journalists, including television newsman Roger Mudd and David S. Broder of The Washington Post.

White and his wife sat in a box with NYNEX vice president of external affairs Ivan Seidenberg and his wife; O'Connor and her husband sat with NYNEX general counsel Raymond Burke and his wife; and Stevens and his wife sat with Sen. Brock Adams (D-Wash.) and his wife, a NYNEX spokesman said.

One source familiar with the invitations said it was routine to invite justices to events such as the ballet. But Stephen Gillers, who teaches legal ethics at New York University Law School, said the justices' presence at the ballet was "insensitive and foolish at best and unethical at worst. It was wrong period, flat, no contest."

Gillers cited the 1977 case of a New York state trial judge who accepted a stay at a Catskill Mountain resort paid by a law firm headed by a friend of the judge. The judge was censured, Gillers said, "even though there was no evidence that the judge was influenced."

The ABA Code of Judicial Conduct, which is binding on lower court judges but not the Supreme Court, says that "a judge or a member of his family residing in his household may accept . . . {a} gift, bequest, favor, or loan only if the donor is not a party or other person whose interests have come or are likely to come before him."

But Yale Law School professor Geoffrey C. Hazard Jr. noted that another provision in that same section of the code says a judge "may accept ordinary social hospitality."

The key question, he said, is ensuring that the judge's conduct not give an appearance of impropriety. In writing the code "we couldn't resolve whose social perception ought to count," he said. Hazard said it could be argued that the ballet outing was, "in a sense, a social event {and was} helping the ballet."

The justices' attendance, was "probably within the rules," he said, but it may not generate a "good perception." "When the hospitality is afforded by a private party as opposed to the government or a civic organization or the bar," he said, "then public unease is quite rightly increased. If the private person is one who could be a litigant," he said, "then the discomfort is increased" even further.

The problem with such broad guidelines is that there are "different sensitivities" held by different groups, he said. "Some who move in high business or government circles say, 'Why not, it is just another concert,' " Hazard said. "But others, such as ordinary blue collar people, see it as 'pal-ing around' with the money people."

Staff member Moira Mulligan contributed to this report.