The U.S. Supreme Court yesterday awarded victory in a six-year-old legal battle to Grendel's Den restaurant in Harvard Square and its attorney. Harvard Law Professor Lawrence H. Tribe '62, invalidating a Massachusetts law that gave churches a veto power over liquor licenses for nearby businesses.

In an 8 I decision, the Court ruled unconstitutional a state law allowing churches to block liquor licenses for businesses within 500 feet.

Grendel's Den went to court with Tribe's aid when the Holy Cross Armenian Church blocked it from obtaining a liquor license in 1977. Lower courts struck down the law as unconstitutional, and yesterday, the nation's highest court agreed in a majority opinion written by Chief Justice Warren E. Burger.

Grendel's Den faces Winthrop St. and the Holy Cross Church faces Mt. Auburn St. but the backs of the two buildings are less than 10 feet apart.

Writing for the Court Burger said that the veto provision "substitutes the unilateral and absolute power of a church for the reasoned decision-making of a public legislative body acting on evidence and guided by standards."

Tribe, who argued the case before the Supreme Court in October, said yesterday that as a result of the decision, restaurants like Grendel's in Boston and around the country no longer need to go through the processes of convincing religious authority."

Now Tribe said, it is "enough to convince civil authorities."

Grendel's Den co-owner, Herbert Kuelzer, said yesterday be expects to receive a license before the end of the month.

A spokesman for the church yesterday issued a statement that "the Supreme Court of the land has spoken, and [the church] will comply immediately and completely."

Burger wrote that "the challenged statute thus enmeshes churches in the process of government and creates the danger of political fragmentation and divisiveness along religious lines."

"Few entanglements could be more offensive to the spirit of the Constitution," Burger added.

Justice William H. Rehnquist dissented, noting sarcastically that the decision proves that like "great" cases and "hard" cases, "silly cases make had law."

Rehnquist also stated that Massachusetts could flatly prohibit liquor licenses for any establishment located near a place of worship. Such a flat ban, he said, is even more protective of churches and more restrictive of liquor sales.

The Massachusetts law also allows such veto power over liquor licenses to schools within 500 feet of a license-seeker, but yesterday's Supreme Court ruling did not involve that aspect of the law.

Herbert Kuelzer and co-owner Susan Kuelzer popped a champagne cork in Tribe's Harvard Law School office yesterday after receiving news of the decision.

Tribe said that the decision reaffirms the fundamental American view that "churches cannot be given governmental power, coercive power, power to make decisions about lives of people other than their own members."

Susan Kuelzer said that when she first applied for a liquor license, "we saw everybody else getting them [and] we thought we would too.

"So, when we applied and were turned down, we said, O.K. that's not fair."

Between 1971 when Grendel's Den opened and 1976 at least 10 other restaurants near the Holy Cross Church applied for licenses without intervention by church officials, Susan Kuelzer said.

The church spokesman, Rev. Peter V. Conley of the Roman Catholic Archdiocese of Boston, said yesterday that the veto issue "has never been a priority item for the Archdiocese of Boston. It has been a matter of one parish addressing its own local problems."

The Kuelzers said they plan to build a bar in the basement portion of the restaurant, an addition which they expect to increase business.