With Chief Justice William H. Rehnquist sidelined by illness for a second straight day, the Supreme Court turned its attention to a case of racial segregation in prison yesterday as an attorney for an African American inmate in California urged the justices to overturn a state policy that places new prisoners in cells according to their race.

California says that its policy, which is unwritten and unique in the nation, does not violate the Constitution because it is necessary to prevent gang-related interracial violence and because the separation of races occurs only during the prisoners' first 60 days of incarceration or when they are being transferred between prisons.

But at yesterday's oral argument, Bert H. Deixler, representing inmate Garrison Johnson, noted that the court has already said any race-based government policy has to be subjected to "strict scrutiny," and he contended that California's justifications cannot pass that stringent test.

The state has "effectively erected 'Whites Only,' 'Blacks Only' and 'Hispanics Only' signs over the portal of California prisons," Deixler said.

Deixler had the support of the Bush administration. Acting Solicitor General Paul D. Clement said the case "presents this court with an opportunity to reaffirm that all government policies based on race should be subject to strict scrutiny."

Under the policy in question, pairs of newly arrived blacks, whites and Latinos are put in separate two-man cells until prison authorities have had 60 days to determine which of them, if any, is a member of one of California's racially distinct gangs, such as the black Crips or the white Aryan Nations.

The court banned permanent racial segregation in prisons in 1968.

Arguing for the state, California Senior Assistant Attorney General Frances T. Grunder told the court that the case was not about racial discrimination but rather about the precautions that authorities must take to protect all inmates, regardless of race.

"The reality is that in prison people are pressured to join gangs and hang with your own," she told the court. "The racial pressures in prison are very, very severe."

She urged the court to analyze the case according to its 1987 ruling that permits states to impinge on some prisoners' constitutional rights if there is a legitimate penological reason to do so.

The California policy received a relatively sympathetic hearing from Justice Antonin Scalia, who asked Deixler: "What is sacrosanct about the right not to be subject to racial stereotyping? People in prison give up lots of rights."

Deixler replied that race-based government policies are presumed unlawful and need to be strongly justified. He noted that California is the only state that uses such a policy, suggesting that it is not necessary to maintain security if other states could get along without it.

Justice Ruth Bader Ginsburg seemed skeptical of the state's justifications.

She asked Grunder about a study of Texas prisons that showed there was less violence in racially mixed prison populations.

Grunder responded that the study did not cover inmate reception centers, which is the only part of the California prison system where the approach of racial separation is employed.

The case is Johnson v. California, No. 03-636. A ruling is expected by July.