Judge Joseph Wapner, a no-nonsense California jurist who embodies the law and dispenses justice five times a week in "The People's Court," a television series, issued an out-of-court opinion yesterday in what might be called the case of the Maryland state Senate election.

Wapner, who said he flew in from Los Angeles for the weekend for the event, attested yesterday to the "honesty" and "integrity" of Del. Ida G. Ruben (D-Montgomery) at a fund raiser for Ruben, who is running for the state Senate from the 20th District in Montgomery County.

However, Wapner, who has retired as presiding judge of the Los Angeles Superior Court, declined to participate in a "mock trial" the Ruben campaign had planned for the gathering at the Silver Spring Holiday Inn.

He told a reporter that he did not want to do anything "to tarnish my image, even at a function like this when it's all in fun."

Wapner, whose televised trials may be seen here five mornings a week on WJLA (Channel 7), said, "I've turned down 'Saturday Night Live,' I've turned down 'The Love Boat' . . . . I'm a judge, I'm not an actor."

A stand-in played the judge yesterday in a skit billed as "The Trial and Tribute in the Case for Ida G. Ruben."

Wapner said he and his wife met Ruben and her husband, Montgomery Circuit Court Judge L. Leonard Ruben, during a trip here three years ago.

"We just instantly liked each other," he said. "We just clicked."

Wapner said that when he learned that Ida Ruben was running for the state Senate he volunteered to help in any way he could, and Ruben took him up on the offer.

Ruben, chairwoman of the county House delegation, is pitted against another Democratic House incumbent, Diane Kirchenbauer, in what is expected to be a hard-fought primary election race for the seat being vacated by 8th District congressional candidate Stewart Bainum Jr.

Kirchenbauer last night called events such as yesterday's "irrelevant to the outcome of the election."

"I think the voters will make their decision based on the discussion of issues, and things much more substantive than having a celebrity fund raiser," she said.

About 200 Ruben supporters paid $25 each to attend yesterday's fund raiser. About 80 persons paid $150 each to attend a Ruben fund raiser Friday night at which Wapner was a guest.

Ruben campaign treasurer Herb Gordon estimated that about $75,000 has been raised for the election effort, about three-quarters of the amount that Ruben supporters estimate is needed.