The Supreme Court yesterday strongly backed the power of Congress to adopt affirmative action programs, ruling that federal minority preference plans do not have to be aimed at making up for past discrimination or meet the same stringent tests as state and local programs.

The 5 to 4 decision, upholding the constitutionality of two Federal Communications Commission minority preference plans, represented a surprise victory for civil rights groups.

The court has grown increasingly hostile in recent years to the idea of giving preference to minorities. Last year, in a decision throwing out Richmond's minority set-aside program for city contracts, the justices curtailed the power of states and localities to adopt affirmative action programs not based on clear proof of past discrimination. Civil rights groups had feared the court might use the FCC cases to cut back on congressional authority as well.

Instead, in an opinion by Justice William J. Brennan Jr. on the last day of the 1989-90 term, the court reaffirmed and appeared to extend a 1980 ruling, Fullilove v. Klutznick, which upheld the constitutionality of a congressional program setting aside 10 percent of federal construction grants for minority businesses.

In ruling yesterday that promoting diversity in broadcast programming was sufficient justification for the minority preferences, Brennan said the assumption that minority ownership of stations would result in more diverse programming did not represent "impermissible stereotyping" but a reasonable overall assumption.

"While we are under no illusion that members of a particular minority group share some cohesive, collective viewpoint, we believe it a legitimate inference . . . to draw that as more minorities gain ownership and policy making roles in the media, varying perspectives will be more fairly represented on the airwaves," Brennan said.

He said that although non-minority firms might suffer as a result of the policies, the burden on them was "relatively light."

Justices Byron R. White, Thurgood Marshall, Harry A. Blackmun, and John Paul Stevens joined in yesterday's decision.

"This exceeded our wildest expectations. On affirmative action, we are a million percent better off today than we were yesterday and 20 million percent better off than we expected to be," said Andrew Jay Schwartzman of the Media Access Project, which had filed a friend-of-the-court brief defending the FCC policies.

The four dissenters, in an opinion by Justice Sandra Day O'Connor, said the ruling "marks a renewed toleration of racial classifications" and "permits distinctions among citizens based on race and ethnicity which the Constitution clearly forbids."

Justice Anthony M. Kennedy, in an even more strongly worded dissent joined by Justice Antonin Scalia, accused the court of returning to the discredited days of Plessy v. Ferguson, the 1896 case upholding "separate but equal" facilities. He compared the justifications for the FCC preference policies to those underlying the South African apartheid system of racial separation.

The ruling in yesterday's case, Metro Broadcasting v. Federal Communications Commission, was the first time a majority of the court has found that minority preference plans may be justified by a goal other than remedying past discrimination -- in this case, promoting the diversity of broadcast programming.

The court also said such programs are constitutional so long as "they serve important governmental objectives . . . and are substantially related to the achievement of those objectives."

The Bush administration had argued that congressional programs had to meet the far higher "strict scrutiny" test that applies to state and local preference plans. The "strict scrutiny" test requires that such programs be "narrowly tailored" to serve a "compelling" government interest.

Arguing against the constitutionality of the FCC policies, the administration had said the diversity rationale -- "the idea that the government has a compelling interest in promoting viewpoints identified with specific racial or ethnic groups" -- was "deeply troubling, and appears to boil down to the type of racial stereotyping that is anathema to basic constitutional principles."

Although the court rejected both those arguments, the impact of yesterday's ruling was somewhat complicated by a separate concurring opinion by Stevens. Stevens, who dissented from the 1980 decision upholding the set-aside program in Fullilove and joined the majority in striking down the Richmond ordinance last year, stressed the importance of diversity and said he was "convinced" that racial classifications were allowed "only in extremely rare situations."

As a result, it was not certain what test the court would apply to judge the validity of an array of other congressionally enacted preference plans, which include Small Business Administration loan programs for minority businesses, Education Department grants to minority college and graduate students, and Transportation Department set-asides for federally funded highway and mass transit projects.

"It certainly, I think, is the surprise of the term. Its potential is very sweeping," said Bruce Fein, a former FCC general counsel who opposed the preference plans. But, he said, "Whether or not they will carry that {analysis} over in blinking at race preferences when it comes to contracts and hiring {justified as remedial measures} is still uncertain."

At issue in yesterday's ruling were two FCC policies designed to boost minority ownership of broadcast stations and thereby increase the diversity of programming broadcast on the nation's airwaves. As of 1986, minorities owned 2.1 percent of the country's more than 11,000 radio and television stations.

Under one policy, the FCC in awarding broadcast licenses gives extra credit to minority-owned firms. In the other, such firms get the first shot at buying, at a reduced price, television or radio stations whose owners risk losing their licenses.

Non-minority firms that lost out on licenses challenged both the policies as a violation of the constitutional guarantee of equal protection.

The federal appeals court here upheld the policy of giving "enhancement credits" to minorities and said the FCC was justified in denying a license to Metro Broadcasting for a television station in Orlando, Fla., in favor of a competitor owned by three Hispanics.

However, a different panel of the same court struck down the "distress sale" policy in a case from Connecticut. It said a Hartford businessman, Alan Shurberg, should have been allowed the chance to purchase a local television station.

The justices upheld both FCC policies in a single opinion. Brennan, writing for the majority, said it was "of overriding significance in these cases that the FCC's minority ownership programs have been specifically approved -- indeed, mandated -- by Congress."

Congress is deemed to have more power than state and local governments in the affirmative action area because of the authority granted to it by the Constitution.

The FCC considered abandoning both policies during the Reagan administration but Congress blocked it from taking such action. Brennan cited those actions, as well as the earlier "long history of congressional support" for the policies.

In her dissenting opinion, O'Connor said the idea of a "benign" racial classificaiton "is particularly troubling" and "a contradiction in terms."

Kennedy and Scalia were even more upset. "Perhaps the Court can succeed in its assumed role of case-by-case arbiter of when it is desirable and benign for the government to disfavor some citizens and favor others based on the color of their skin," Kennedy said.

"But history suggests much peril in this enterprise, and so the Constitution forbids us to undertake it. I regret that after a century of judicial opinion we interpret the Constitution to do no more than move us from 'separate but equal' to 'unequal but benign.' "