Charlie Savage / New York Times News Service

WASHINGTON — Some Republican lawmakers want President Barack Obama to declare the surviving Boston bombing suspect an enemy combatant in order to question him without a lawyer and other protections of the criminal justice system, intensifying a recurring debate over how to handle terrorism cases arising inside the United States.

But while the suspect, Dzhokhar Tsarnaev, a naturalized U.S. citizen, is a Muslim, there is no known evidence suggesting that he is part of al-Qaida. The United States is engaged in an armed conflict with al-Qaida, not all Muslim extremists. As a result, the dispute is pushing beyond familiar arguments and into new territory.

Sen. Lindsey Graham, R-S.C., is the earliest and most vocal proponent of declaring Tsarnaev an enemy combatant. Others include Sens. Kelly Ayotte of New Hampshire, Saxby Chambliss of Georgia, and John McCain of Arizona, as well as Rep. Peter T. King of New York, all also Republicans.

The Obama administration has said that it thinks terrorism suspects arrested inside the United States should be handled exclusively in the criminal justice system. It has indicated no intention to do otherwise in Tsarnaev’s case, but the issue is taking on political currency, underscoring a major divide on national-security legal policy.

Sen. Carl Levin, D-Mich., who is chairman of the Senate Armed Services Committee, said in a statement that the laws of war do not apply to Tsarnaev and that there is so far no evidence that he was “part of any organized group, let alone al-Qaida, the Taliban, or one of their affiliates — the only organizations whose members are subject” to detention as part of the war.

“In the absence of such evidence, I know of no legal basis for his detention as an enemy combatant,” Levin said. “To hold the suspect as an enemy combatant under these circumstances would be contrary to our laws and may even jeopardize our efforts to prosecute him for his crimes.”

In an interview, Graham acknowledged that if no evidence emerges linking Tsarnaev to al-Qaida then he should not continue to be held as an enemy combatant. But he argued that, given the need to swiftly find out if Tsarnaev knows of other planned attacks or terrorist operatives, the government can and should hold him as a combatant while it searches for any such links.

“You can’t hold every person who commits a terrorist attack as an enemy combatant, I agree with that,” Graham said. “But you have a right, with his radical Islamist ties and the fact that Chechens are all over the world fighting with al-Qaida — I think you have a reasonable belief to go down that road, and it would be a big mistake not to go down that road. If we didn’t hold him for intelligence-gathering purposes, that would be unconscionable.”

Graham said 30 days of confinement and interrogation as an enemy combatant would be an appropriate amount of time to allow the government to look for evidence that would justify his continued detention under the law of war.

Beyond the absence of known links between Tsarnaev and al-Qaida, it is also unclear whether the Constitution permits the government to hold citizens arrested on domestic soil as enemy combatants. While Graham believes it would be lawful, other lawmakers disagree. Neither Congress nor the Supreme Court has resolved the question.

During the Bush administration, the Supreme Court upheld the indefinite military detention of Yasser Hamdi, a citizen who was captured carrying a weapon on the Afghanistan battlefield.

But the court never resolved the case of another American, Jose Padilla, whom the Bush administration held as an enemy combatant for several years after his arrest in Chicago. Two different federal appeals courts disagreed about whether it was lawful to hold someone like Padilla in indefinite detention without trial, and the Bush administration transferred him back to the civilian court system before the Supreme Court took up the case.

Graham said the purpose of holding Tsarnaev as a military detainee would be to question him at length without any lawyer. Though the Obama administration has said it would use a public-safety exception to the Miranda rule to question him for a period without warning him of his rights to remain silent and have a lawyer, Graham said that would at best gain only a few days before a lawyer intervened.

Graham also acknowledged that ultimately Tsarnaev must be transferred back to the civilian criminal justice system for prosecution, since the statute authorizing military commissions — which he helped write — does not apply to U.S. citizens.

Questions for suspect

Federal prosecutors Sunday were preparing to file charges against the surviving suspect in the Boston Marathon bombing, even as he remained under heavy guard at a local hospital amid questions about whether authorities would be able to interrogate him. Dzhokhar Tsarnaev, 19, was in critical but stable condition with a gunshot wound to the neck, Boston police said Sunday, and federal and local officials said they were unsure he would be able to talk again. “We don’t know if we’ll ever be able to question the individual,” Boston Mayor Thomas Menino said Sunday.

Rebels deny involvement — Rebels in Russia’s North Caucasus region denied any link to the April 15 attack on the Boston Marathon in a statement posted on the website. “The Caucasian Mujahedeen are not fighting with the United States of America,” according to the statement, which was attributed to unidentified Mujahedeen commanders in Dagestan. “We are at war with Russia, which is responsible not only for the occupation of the Caucasus but also for heinous crimes against Muslims.”

— From wire reports