The Supreme Court, in a major defeat for religious fundamentalists, voted 7 to 2 yesterday to strike down as unconstitutional state laws that require public schools to teach "creation science" if they teach the theory of evolution.

The First Amendment's requirement of separation of church and state, Justice William J. Brennan Jr. said for the majority, "does not permit the state to require that teaching and learning must be tailored to the principles or prohibitions of any religious sect or dogma."

The ruling struck down a 1981 Louisiana "balanced treatment" law, which demanded "equal time" for teaching creation science -- the evidence supporting the "abrupt appearance" of most life forms on Earth -- whenever a school teaches evolution.

Brennan, calling the state legislature's claim to a secular purpose a "sham," said the law in effect required teaching of a religious belief, not a scientific study.

The tenets of creationism closely resemble the Bible's account of creation.

"The preeminent purpose of the Louisiana legislature was clearly to advance the religious viewpoint that a supernatural being created humankind," Brennan said.

The law "violates the Establishment Clause of the First Amendment," he said, "because it seeks to employ the symbolic and financial support of government to achieve a religious purpose."

Justice Antonin Scalia, joined by Chief Justice William H. Rehnquist in dissent, said the court should not have struck down the law. "The people of Louisiana, including those who are Christian fundamentalists, are quite entitled, as a secular matter, to have whatever scientific evidence there may be against evolution presented in their schools."

The decision undercuts a century-long effort by fundamentalists to stop the teaching of evolution in the public schools. A ruling in favor of the fundamentalists, lawyers on both sides agreed, would have spurred efforts in dozens of states to pass similar laws.

Opponents of creation science hailed the outcome. {Story, Page A12.} American Civil Liberties Union lawyer Steven Shapiro called it "the legal end of the creationism movement." Jay Topkis, who argued the case for the ACLU at the Supreme Court, said the ruling "says to anybody what everybody knows, that creationism is religion. Legislators in other states are not likely to be fooled" into passing similar laws, he said.

Louisiana state Sen. Sidney Nelson, who led the opposition to the law, agreed that the ruling "is the death knell for this type of legislation," probably nationwide, but "certainly in Louisiana. The fact that the vote is 7 to 2 would dissuade others," he said.

And Bruce Fein, an attorney with the conservative Heritage Foundation who sided with the law's proponents, agreed. "This {decision} is just telling them {creation science proponents} to forget it," Fein said. "The court went out of its way to say that if you have a statute that is the product of 'fundamentalist fervor' they are going to throw it out."

The strong rejection of the Louisiana law also may undermine a challenge by conservative Christian parents charging in an Alabama lawsuit that textbooks there unconstitutionally promoted the "religion" of secular humanism. Lawyers on both sides said the decision would not directly affect a case in Tennessee, where fundamentalist parents argue that their children should be allowed to opt out of certain classes.

But the creationists' lead attorney, Wendell R. Bird, who argued the case at the high court, said the ruling will not stop the creation science movement. "The justices did not say it was inherently unconstitutional to teach creation science along with evolution, just that the particular purpose of the Louisiana legislature" was unconstitutional, he said.

"I would not expect the ruling to stop {efforts to promote} the teaching of creation science," Bird said. "Eighty-six percent of the public favors 'balanced treatment' laws," and "86 percent of the public can't be stopped in the long run, especially given the age of the justices {with} four in the majority over 75 years old. You can't stop anything so broadly supported, only delay it," he said.

The bill's sponsor, former state senator Bill Keith, said he is "saddened and frustrated, but we are going to go on." He said creationist supporters were looking at the possibility of introducing similar, but not identical, legislation in California, Arizona, Florida and perhaps Texas.

Yesterday's decision, Edwards v. Aguillard, came in a case in which the anti-evolutionists found themselves in the best legal position they had been in since 1925, when John Scopes was convicted for teaching evolution in the famous "monkey trial" in Tennessee.

A federal district court judge struck down the Louisiana law in 1985 without ordering a trial. A three-judge appeals court panel agreed, but seven of the circuit's 15 judges joined in an opinion that the equal-time provision was constitutional.

That one-vote loss was the closest fundamentalists have come to victory in the federal courts. In this case, their attorneys had hoped for, if not an outright win, then at least a ruling by the high court sending the case back to the district court for a full trial.

Brennan said no trial was necessary. He was joined by Justices Thurgood Marshall, Harry A. Blackmun, Lewis F. Powell Jr., John Paul Stevens and, for the most part, Sandra Day O'Connor. Justice Byron R. White concurred.

The district judge was correct to strike down the law without a trial, Brennan said, because there was no dispute over the essential facts in the case. The judge's ruling "rested on the plain language of the creationism act, the legislative history and historical context of the act, the specific sequence of events leading to the passage of the act" and other facts demonstrating that its passage was religiously motivated.

Brennan rejected arguments by creation science advocates who said the law's purpose was not to promote religion but to protect academic freedom and ensure fair treatment for all views. Backers said the law ensured that students learn the scientific evidence for the creation theory whenever they are taught about evolution.

Evolution theory contends that life forms became increasingly complex over a period of billions of years; simple one-celled animals "evolved," eventually, to human beings.

"The goal of providing a more comprehensive science curriculum is not furthered either by outlawing the teaching of evolution or by requiring the teaching of creation science," Brennan said.

The Lousiana law, he said, "does not serve to protect academic freedom, but has the distinctly different purpose of discrediting evolution by requiring it to be counterbalanced at every turn with the teaching of creation science."

Brennan said "the goal of basic 'fairness' is hardly furthered by the act's discriminatory preference for the teaching of creation science and against the teaching of evolution."

Powell, in a separate concurrence joined by O'Connor, said that when both the district and appeals courts "are unable to discern an arguably valid secular purpose, this court normally should hesitate to find one. My examination of the language and the legislative history of the Balanced Treatment Act confirms that the intent of the Louisiana legislature was to promote a particular religious belief . . . . It is clear that religious belief is the Balanced Treatment Act's 'reason for existence,' " Powell said. "The tenets of creation science parallel the Genesis story of creation, and this is a religious belief. No legislative recitation of a supposed secular purpose can blind us to that fact."

Scalia, in dissent, said he was "astonished by the court's unprecedented readiness" to reach the conclusion that the law was a "sham enacted to conceal the legislators' violation of their oaths of office." He said the majority showed "an instinctive reaction that any governmentally imposed requirements bearing upon the teaching of evolution must be a manifestation of Christian fundamentalist repression.

"In this case, however, it seems to me the court's position is the repressive one." He said "that illiberal judgment, that Scopes-in-reverse, is ultimately the basis on which the court's facile rejection of the Louisiana legislature's purpose must rest."