The highest court yet to consider the legality of the FBI's controversial Abscam investigation gave it its blessing yesterday.

In a 7-to-2 decision, the full U.S. 3rd Circuit Court of Appeals reinstated the convictions of two Philadelphia city councilmen who had been recorded on videotape taking cash from undercover FBI agents.

The trial judge had overturned the jury's verdict in 1980, but yesterday the appeals court ruled that the jury was right in deciding the defendants were predisposed to commit a crime and therefore had not been entrapped by the agents, who posed as representatives of a fictitious Arab sheik. The court also ruled that the councilmen's constitutional rights to "due process" hadn't been violated by improper FBI conduct.

Sen. Harrison A. Williams Jr. (D-N.J.) and six House members who also were convicted on Abscam corruption charges have raised entrapment and due-process agruments similar to those rejected yesterday. Williams' sentencing is set for Tuesday and he faces an expulsion vote by the Senate later this month.

The Philadelphia case involves former City Council president George X. Schwartz and former council majority leader Harry P. Jannotti. They were convicted in September, 1980, on conspiracy charges after agreeing to use their influence to help the "sheik's" investments in the city.

Richard Sprague, Schwartz's lawyer, said his client will appeal the decision to the Supreme Court. "We hope the Supreme Court will recognize this as the very important case it is," he said.

The trial judge, John P. Fullam, threw out the convictions in November, 1980, saying the defendants' conduct was disgusting, but finding it was more important to protect "the rights of all citizens not to be led into criminal activity by governmental overreaching . . . . "

The 70-page majority opinion was written by Judge Delores Sloviter. She said the dissenting opinion "simply glosses over the salient fact, which is inescapable because of the videotape record: defendants accepted the money readily, unprotestingly, even casually, without ever once attempting to use their consummate political skill to say, as diplomatically as the circumstances required, 'Thanks, but no thanks.' "

Judge Ruggiero Aldisert said in the 35-page dissent that "the division of the court in this extremely important entrapment case reflects fundamental and irreconcilable differences in the values attached to two primary integrants of the American tradition of justice: to what extent should federal judges assume the responsibility for protecting American justice traditions, and to what extent should federal judges endorse tactics of the kind used by the FBI in this case?"

"The majority opinion read like a paean to the FBI for its conduct in this case; but as an American citizen and as a federal judge, I find that conduct revolting."