The Supreme Court ruled Monday that cities must have specific evidence of racial discrimination before they can adopt programs that require a percentage of construction contracts to be awarded to minority businesses.

The 6-3 ruling by the court in a case from Richmond, Va., is a major blow to muncipalities trying to end discrimination in the construction business and will likely upset minority business set-aside programs across the country. Many of those plans, like the one from Richmond, have been enacted on a general belief that there has been discrimination.The court's ruling also illustrates the legacy of the Reagan administration, which has repeatedly urged the court to overturn such affirmative action plans. Reagan appointees made up the core of the majority in the ruling.

"While there is no doubt that the sorry history of both private and public discrimination in this country has contributed to a lack of opportunities for black entrepreneurs, this observation, standing alone, cannot justify a rigid racial quota in the awarding of public contracts in Richmond, Va.," Justice Sandra Day O'Connor said for the majority.

She said that an "amorphous claim that there has been past discrimination in a particular industry cannot justify the use of an unyielding racial quota."

O'Connor was joined by Chief Justice William Rehnquist and Justice Byron White, John Paul Stevens, Antonin Scalia and Anthony Kennedy.

Justices Thurgood Marshall, William Brennan and Harry Blackmun dissented from the ruling with Marshall calling the decision "a deliberate and giant step backward in this court's affirmative action jurisprudence" and Blackmun declaring, "The court today regresses."

Marshall's dissent, which Blackmun and Brennan joined, was a passionate defense of the Richmond set-aside program and a point-by-point rejection of the majority's analysis.

"Cynical of one municipality's attempt to redress the effects of past racial discrimination in a particular industry, the majority launches a grapeshot attack on race-conscious remedies in general," Marshall wrote in the 34-page dissent.

"The majority's unnecessary pronouncements will inevitably discourage or prevent governmental entities, particularly states and localities, from acting to rectify the scourge of past discrimination."

Blackmun said, "I never thought I would live to see the day when the city of Richmond, Va., the cradle of the Old Confederacy, sought on its own, within a narrow confine, to lessen the stark impact of persistent discrimination. But Richmond acted.

"Yet this court, the supposed bastion of equality, strikes down Richmond's efforts as though discrimination had never existed or was not demonstrated in this particular litigation. ... So the court today regresses."

Henry Marsh III, a Richmond city councilman and former mayor who co-sponsored the 1983 ordinance, said, "It's a tremendous setback. In the past, the court has ruled that race-conscious remedies could be used to correct past discrimination, as was demonstrated in this case." He said he believed an effort will be made to enact a new ordinance that would pass muster with the high court.

Jerry Lederer, counsel for the U.S. Conference of Mayors, said, "Certainly, the opinion itself will cause judicial review of other set-aside programs ... and certainly we're not happy. If you look at what's been happening down in Miami, for instance, you've got an awful lot of racial unrest down there because people aren't part of economic opportunity.

Randy Arndt, speaking for the National League of Cities, said, "We are disapppointed in that there was ample demonstration of a problem that needed to be addressed."