The Supreme Court reversed in an unsigned opinion. It said the Sixth Circuit had “framed the issue at too high a level of generality.” There was, the opinion said, no precedent addressing “the specific question presented by this case.”

“None of our holdings,” the opinion said, framing the issue much more narrowly, “address counsel’s absence during testimony that is irrelevant within the defendant’s own theory of the case.”

In a second characteristic move, the opinion said it was agnostic about whether Mr. Donald’s constitutional rights had indeed been violated when his lawyer decided to skip part of the trial. All it decided under the 1996 law, the opinion said, was that the question was an open one.

That kind of reasoning, Judge Reinhardt wrote, has stunted the development of constitutional law and has “unfortunate parallels” in another body of decisions, those involving civil claims against government officials accused of misconduct.

Such officials are generally entitled to qualified immunity, which requires plaintiffs to show that the officials had violated “clearly established” legal principles. Here, too, the court has engaged in a kind of semantic leapfrog, often deciding that a right had not been clearly established without saying whether that right was in fact required by the Constitution.

An unsigned decision last month illustrates the point. The family of a mentally troubled man, Christopher Barkes, sued Delaware prison officials for not doing enough to keep Mr. Barkes from killing himself while in custody for violating his probation.

A divided panel of the Third Circuit, in Philadelphia, rejected the officials’ claim to qualified immunity. Understanding the legal terrain, the majority noted that “the ‘clearly established’ game is won or lost on how broadly or narrowly one defines the right at issue.”