Legal experts say Monday's plea agreement between U.S. government prosecutors and Taleban sympathizer John Walker Lindh offers benefits for both sides in the case. But because there will be no trial, some important legal questions have been left unresolved.

The plea agreement is a good deal for John Walker Lindh. He avoids spending the rest of his life in prison and is likely to receive a 20-year jail term when he is sentenced in October.

It is a good deal for the government as well. Prosecutors can now avoid potentially embarrassing revelations about Lindh's treatment by U.S. troops in Afghanistan and will not have to compromise intelligence sources who might have been required to testify had there been a trial.

But the lack of a trial means some key legal questions related to the U.S. government's war on terrorism will not be resolved.

Among them is whether the president has the authority to designate an American citizen an unlawful combatant with no opportunity for review by the U.S. court system.

That is a crucial issue for legal experts like Robert Hirshon, the president of the nation's largest lawyers group, the American Bar Association. "The ability of the executive branch to label an American as an unlawful combatant and therefore say that that American no longer has the protections of our Constitution," he said. "We are very concerned about that and we have a group that is studying that issue right now."

Lindh fell into the category of an unlawful combatant when he was captured along with other Taleban and al-Qaida fighters in Afghanistan. But his lawyers argued that the confessions extracted from him were illegal because, as an American citizen, he should have been warned that his statements might be used against him in court.

Any ruling in the Lindh case could have had direct relevance to the case of Jose Padilla, another U.S. citizen who was arrested in May for his alleged role in a plot to explode a radioactive so-called dirty bomb in the United States. Mr. Padilla is now in U.S. military custody after being declared an unlawful combatant by President Bush.

Some legal experts believe the government's willingness to enter into a plea agreement with John Walker Lindh could have an impact not only in the Padilla case, but also in the case of American-born Yaser Esam Hamdi, who has also been declared an enemy combatant.

"The one impact that this may have on others, I suppose, is that this could embolden others," said Eric Muller, a specialist in international law at the University of North Carolina. "If what the government is doing here is ultimately seen as a sign of weakness or a sign of unwillingness to go public with the circumstances of these people's apprehension, if it looks like the government is the one that is blinking in this standoff, then that might embolden other people in similar situations to try to demand better deals from the government than they might currently be getting."

The government has yet to announce whether it will seek criminal charges against either Mr. Padilla or Mr. Hamdi.