Two federal judges in San Diego ruled yesterday that the new federal sentencing guidelines are unconstitutional, declaring that the commission that wrote them violated the doctrine of separation of powers.

In the first court decision addressing constitutionality of the guidelines, U.S. District Court Judge Rudi M. Brewster said the 1984 law establishing the U.S. Sentencing Commission to write the guidelines is invalid because it "impermissibly designates the commission as part of the judicial branch" and because the seven-member panel includes three federal judges.

A second San Diego judge, John S. Rhoades Sr., later issued a two-page opinion indicating that he agreed with Brewster's reasoning.

The decisions are not binding on other judges. However, they are significant because they are the first on the issue, which has triggered a spate of challenges nationwide.

Brewster said the commission's writing of the guidelines constitutes an "executive function" and that Congress was wrong in labeling the commission part of the judicial branch.

In addition, Brewster said, even if the commission were part of the executive branch, the requirement that three federal judges serve on it would violate the separation of powers by requiring a judge-commissioner to "wear two hats -- one executive and one judicial."

"For federal judges to perform properly, their judicial function must remain impartial and independent," said Brewster, appointed to the bench by President Reagan in 1984. "The independence and impartiality of the federal judicial office is threatened by the mandatory participation of three {federal} judges on the commission."

As a result, he said, "the guidelines, being promulgated and distributed by a constitutionally flawed commission, must be held invalid."

The guidelines took effect Nov. 1 and apply to crimes committed after that date. They were designed to eliminate disparate sentencing of individuals convicted of the same crimes by establishing general sentencing ranges and specific factors for judges to consider in imposing sentences.

Judges are not bound by the guidelines, but they must explain their reasons for any departures, and both government and defendant are given the right to appeal.

"Obviously, this is not anywhere near the last word, but it is an important indication that the challenges are real and substantial as we've contended all along," said Alan B. Morrison of Public Citizen Litigation Group. He argued before Brewster and seven other San Diego judges Wednesday that the guidelines were unconstitutional.

Morrison said the Brewster ruling "is going to throw further chaos into the system because there needs to be an immediate resolution of this constitutional question."

Sentencing Commission Chairman William W. Wilkins Jr., a judge on the 4th U.S. Circuit Court of Appeals, said the ruling is "just the first step in a final resolution of the constitutional issue."

"As all major pieces of legislation have to be tested, the sentencing reform legislation has to be tested," he said. "I am delighted that the ruling has come as quick as it has because we need this issue decided by the United States Supreme Court just as soon as possible."

Wilkins defended the constitutionality of the commission and said he sees no conflict between his two roles.

Justice Department spokesman Terry H. Eastland said, "Obviously, we argued for a different position in the court. This is an important constitutional question, and we will appeal."