The Supreme Court yesterday provided further insulation for union seniority systems against job discrimination claims.

The case stemmed from a two-tiered employment policy in the California brewing industry which, it was alleged, permanently prevented blacks from achieving full job security.

Under the system, only workers employed 45 weeks during a year can obtain the special privileges of full seniority. But full seniority is necessary in order to ever get that much work -- 45 weeks -- since the workers are called in in order of seniority.

In a plurality opinion joined by only four justices, the Supreme Court determined yesterday that the California brewing industry system was a legitimate seniority system exempt by law from the Civil Rights Act.

It overturned a lower court decision to the contrary.

The Supreme Court had already gone on record in support of the seniority exemption written into the civil rights law. The question before it in this case was what is a bona fide seniority system.

Justice Potter Stewart wrote that the California system "does not depart significantly from commonly accepted concepts of seniority" since it does not set up an "educational standard, an aptitude or physical test or a standard that gives effect to subjectivity." It focuses, he said, "on the length of employment" and is therefore exempt from civil rights legislation.

Stewart was joined by Chief Justice Warren Burger and Justices Byron White and William Rehnquist. Justices Lewis Powell and John Paul Stevens did not participate for undisclosed reasons, and Justice Thurgood Marshall, with Justices William Brennan and Harry Blackmun, wrote a dissent.

The California system, Marshall said, has "no relation to principles of seniority." A law "designed to remedy the national disgrace of discrimination in employment should be interpreted generously to comport with its primary purpose," Marshall wrote.

In other decisions yesterday, the court:

Upheld a New York program of financial aid to nonpublic and parochial schools which helps the private institutions meet the costs of obeying certain state education requirements.

Money is provided, for example, for state-mandated pupil testing and reporting requirements under the New York law. The court said yesterday that the program meets its constitutionality test by having a secular purpose that neither "advances nor inhibits religion."

Justice Byron White delivered the opinion in Committee for Public Education and Religious Liberty vs. Reagan and was joined by Chief Justice Burger, and Justices Stewart, Powell and Rehnquist. Justices Blackmun, Brennan, Marshall and Stevens dissented.

Ruled that suits against individual federal government officials must be filed in courts geographically convenient to where the defendant lives or where the alledged offense occurred. c

The case involved Vietnam-era suits by antiwar activists against former CIA director William Colby in connection with CIA mail openings and against federal prosecutors and FBI agents in connection with a grand jury investigation there.

In both instances, the suits were brought far from the residences of the officials and from the place where the offenses allegedly occurred.

The court said under the law that this could only be done if the suit were against the U.S. government, which can be sued anywhere in the country.