The ruling "weakens the fundamental protections the double jeopardy clause was intended to provide," he said.

Now, however, "this ruling certainly weakens him," said Dan Clawson, a professor at the University of Massachusetts who teaches labor relations and campaign finance.

A ruling in support of the Pennsylvania law would weaken Roe v. Wade substantially and give states increased latitude to regulate abortions.

His ruling could potentially weaken that case, which is the government's largest criminal tax case ever.

A FEDERAL appeals court ruling issued in New York this month could crucially weaken the multibillion-dollar managed care industry, the H.M.O. trade association contends.

Weakens Argument Other intellectual-property lawyers agreed that the ruling could weaken the notion of look and feel as applied to software programs.

But Justice Stephen G. Breyer, writing for the dissenters, said the court's ruling "weakens, perhaps destroys, much of the practical value" of the knock-and-announce protection.

Some say the ruling weakened, if not gutted, the Government's case.

But Mr. McCain and the other principal sponsors of the law said the rulings by the commission seriously weakened the force of the legislation.