A federal appeals court refused yesterday to reconsider its ruling setting aside former White House aide Oliver L. North's convictions in the Iran-contra scandal.

The three-judge panel that made the ruling last July by a vote of 2 to 1 reaffirmed it in another split vote. At the same time, the U.S. Circuit Court of Appeals denied a request by independent counsel Lawrence E. Walsh for reconsideration by the full 12-judge court.

Walsh said he would "in all probability" take his appeal to the Supreme Court. Last July's ruling flatly reversed one of the three guilty verdicts against North and set aside the others for an elaborate set of hearings that the trial judge had deemed unnecessary.

In the decision yesterday, Judges David B. Sentelle and Laurence H. Silberman said North had been denied "a hearing to which the Constitution entitled him" and that none of the difficulties Walsh faced in meeting the court's standards could justify that denial.

Unless the ruling is overturned, North is entitled to a "witness-by-witness {and} if necessary, line-by-line and item-by-item" review of both grand jury and trial witnesses to find out whether any of North's widely televised congressional testimony in July 1987 was used against him in his 1989 trial.

The former National Security Council aide gave the testimony under a grant of immunity from prosecution, a grant that Walsh unsuccessfully sought to block.

Walsh had protested that the majority ruling would make it "virtually impossible" to bring a criminal prosecution against anyone who has testified publicly under a grant of immunity.

Chief Circuit Judge Patricia M. Wald agreed with Walsh in a dissenting opinion, saying her colleagues had set down "practically unattainable" requirements that go far beyond the requirements of a landmark 1972 Supreme Court ruling on the issue, Kastigar v. U.S.

She argued that Walsh's prosecutors and U.S. District Judge Gerhard A. Gesell, who presided at the trial, had been diligent enough to avoid use of North's immunized testimony and that there should be different rules for "prosecutorial exposure" on the one hand and "witness exposure" on the other.

The majority yesterday rejected the distinction, saying it amounted to a "look ma, no hands" excuse for prosecutors.

Instead, the majority held that Kastigar is "violated whenever the prosecution puts on a witness whose testimony is shaped, directly or indirectly, by compelled testimony, regardless of how or by whom he was exposed to that compelled testimony. . . . The burden of disproving use cannot . . . be shifted onto the defendant."

Sentelle and Silberman also said they thought Wald's dissent exaggerated a prosecutor's difficulties. She said that "if, as my colleagues maintain, this is constitutional territory, then there is all the more reason for the most careful consideration before we lay down absolute and intolerable burdens on the prosecution in a media-dominated age."

North was convicted in May 1989 of obstructing Congress, altering and destroying government documents, and taking an illegal gratuity from one of his confederates.

The panel yesterday withdrew a segment of its July 20 ruling, reversing the guilty verdict on the documents charge on grounds that Gesell had improperly instructed the jury on how to reach a unanimous verdict in that instance. The majority said yesterday that it had misread the trial record and held that the instructions on this point were proper.

The reversal still stands, however, because the majority, again over Wald's dissent, held that Gesell's instructions to the jury on whether North felt authorized by his superiors to destroy the documents were too restrictive. The panel said in July that "subjective knowledge of unlawfulness" was required for conviction.

Judge Ruth B. Ginsburg said she would have granted a rehearing by the full court on this point. She said the July ruling could be used to justify "even a patently unreasonable" claim by a defendant that his actions were legal.