The California Supreme Court, badly damaged by dissension and an unresolved investigation into purported ethical misconduct, has been dealt a new blow by an unexpected ruling that indefinitely suspends the paychecks of the court's seven justices.

The ruling, by Scaramento Superior Court Judge Joseph C. Babich, upheld an 1879 state constitutional provision that prevents a judge from receiving his or her salary if he or she takes more than 90 days to rule after a case is submitted for decision.

For years, this provision has been routinely applied to every court in California except the Supreme Court. The high court has evaded the constitutional provision by using an elastic definition of "submission," in some cases saying submission occurred the day a case was decided.

Judges and lawyers, especially prosecutors, long have grumbled about the double standard. A study this year by the California Commission on Judicial Performance, the body investigating the court, shows that in 1977-78 it took the California Supreme Court an average 209 days to decide a case after argument, compared to an average 98 days for the U.S. Supreme Court.

But few who have been battling for speedier decision-making by the Supreme Court expected Babich, a 1964 appointee of Gov. Edmund G. (Pat) Brown, to do anything about it.

The case urging literal application of the 90-day rule to the Supreme Court was brought by the Law and Order Campaign Committee, the conservative organization that last year opposed the confirmation of Chief Justice Rose E. Bird, and the accepted view was that it was a public relations device to call attention to Supreme Court delays.

Historically, lower court judges -- whose cases are subject to review and being overturned by the state Supreme Court -- have been reluctant to challenge any procedure of the state's highest court.

Babich, however, surprised even the committee by declaring that Supreme Court justices "made up the rules as they go along." He said they were "playing God," and apparently decided, in effect, to play chancellor of the exchequer himself.

On Friday, in compliance with Babich's order, state Comptroller Kenneth Cory asked the justices (who receive $69,396 a year, with Bird getting $73,723) to return their paychecks. He said it would mail no others as long as the order stands. Furthermore, Cory said any appeal of the ruling is up to the individual justices.

The justices also could comply with the 90-day rule, but this would not be easy. Some cases have been pending for more than a year -- one of the reasons the court came under investigation in the first place.

The Commission on Judicial Performance is investigating allegations that the court delayed two controversial decisions until after the 1978 election, in which Bird and three other justices faced confirmation votes. One of these cases, which temporarily set aside the state's "use-a-gun, go-to-prison" law, took 319 days to decide after arguments. The other, which struck down a long Los Angeles custom of displaying a lighted cross on city hall at Christmas, took 438 days to decide.

The investigation has bogged down because one justice, Stanley Mosk, challenged the open proceedings of the commission. Then Justice Frank C. Newman, author of the Los Angeles Christmas cross decision, refused to disqualify himself on Mosk's challenge and delayed the inquiry for weeks until an appeals court finally removed him.

All the attempts to block the investigation have damaged the court as it struggles to regain its once-high reputation. Some legal experts think the court has been irreparably harmed by the commission's public revelations of deep internal feuds, misunderstandings and administrative confusion.

Bird, the center of the storm, was on vacation in Sacramento and unavailable for comment. Her San Jose attorney, Harry Delizonna, observed that Bird had testified before the commission that she was merely following the procedures the court had used for 25 years.

But these procedures face a challenge that has never before confronted the Supreme Court. By striking at the justices' pocketbooks rather than at their testimony, Babich may have accomplished more with his simple ruling than the commission did with its long and detailed investigation into the ethics of the state Supreme Court.

Special correspondent Paul Grabowicz contributed to this report.