Snuffing candles and solemnly blowing a ram's horn in a room at a Holiday Inn in Massachusetts, three rabbis used a text dating from the 1750s to excommunicate several hundred Jews last weekend for alleged Marxist views on Israel and sex.

The mainstream Jewish community reacted with laughter.

"We don't have excommunication anymore," said Rabbi Seymour Siegel, professor of ethics and theology at the Jewish Theological Seminary in New York. "Those three have no status whatsoever."

"I assume it would be rude to laugh," said one of those excommunicated, Nobel laureate Salvador Luria, a biologist at the Massachusetts Institute of Technology. "I was about to open champagne to celebrate."

He added, however, that the action was "an example of the kind of attacks that we people who criticize Israel are exposed to."

One of the excommunicators, Rabbi Marvin Antelman of Newton, Mass., insisted that levity was "100 percent wrong." Calling himself the chief justice of the 13-member Supreme Rabbinical Court of America Inc., set up in 1973, Antelman said the court's action, no matter how unusual, may be reversed only by the chief rabbis of the Ashkenazi and Sephardic communities, who live in Israel.

"We have captured the imagination of the grass-roots Jewish community in the United States and that's what's bothering them," he said of his critics.

Siegel noted that Antelman had formed the court and had named himself chief justice.

Those excommunicated, Antelman said, were guilty of "collaboration with the enemy and committing a traitorous act," either by cosigning a June 20 advertisement in The New York Times or belonging to a liberal group called The New Jewish Agenda, based in New York.

The Times ad, placed by the Ad Hoc Committee in Defense of the Palestinian and Lebanese People, criticized Israel's invasion of Lebanon. The New Jewish Agenda also opposed the invasion, but was singled out for its alleged Marxist ties and for recognizing homosexual rights among Jews, Antelman said.

"This group is adopting the word 'Jewish' to get across a Trotskyite program in defense of the Palestine Liberation Organization," Antelman said.

"You can't be Jewish and homosexual. It's a contradiction in terms. It's an abomination," he continued. "It violates the covenant" of promises between God and the Jews and is "like undoing the circumcision."

Reena Bernards, director of the NJA, called the excommunication "absurd" and said Antelman's group "has been harassing our chapter in Boston." She disagreed that Jewish law is so strict on homosexuals.

Antelman, a chemist who said he is a "circuit-riding rabbi" with no congregation, led Rabbis Jehu Eaves of Boston and Herbert Gilner of Long Island in the excommunication ceremony Sunday at the Tewksbury, Mass., hotel.

Wearing judicial robes before an audience of about a dozen supporters, the three snuffed the candles to symbolize the end of their targets' spiritual lives, using the text of the 1757 excommunication of a Jewish heretical group called the Satanic Sabbatian Frankists in Brode, Poland.

Any three rabbis may constitute a Jewish court, called a Bet Din, but its authority normally extends only over the congregations of the rabbis, and then only if the congregation members agree to it, Siegel said. Excommunication, when done in the Middle Ages, "was always by a recognized ecclesiastical authority . . . but we don't have central authorities now."

He added that he was "sympathetic with the point" Antelman's group was trying to make in opposing the advertisements and the NJA, "but to use this kind of device is outrageous and has no meaning whatsoever."

Linguist Noam Chomsky of MIT, another of those excommunicated, recalled that he shared the honor with the 17th century Dutch philosopher Benedict de Spinoza. "I don't think it will carry much weight in Israel except in very kooky circles," Chomsky said.