Sen. Joe Lieberman introduced legislation on Thursday that would strip Americans of their citizenship if they are arrested overseas for their affiliation with a foreign terrorist organization.
The bill would not apply to Times Square bombing suspect Faisal Shahzad, because the measure is not retroactive. But suspects like Shahzad, who was captured on U.S. soil, could be stripped of citizenship -- although that would be an unlikely scenario for multiple reasons.
Under the bill, Americans captured overseas and found to be connected with a foreign terrorist organization would be stripped of citizenship and could be hauled before a military commission.
"I believe that anyone apprehended and charged with attempt to commit a terrorist act against the United State is effectively a prisoner of war and should be tried by the military system of justice," the Connecticut independent senator said at a news conference flanked by other lawmakers supporting the bill, including Sen. Scott Brown, R-Mass., and Rep. Jason Altmire, D-Pa., who is introducing a companion bill in the House.
"The reason we're doing this, being an American citizen means something," Lieberman said. "To me, somebody who takes up arms against the United States, whether they wear the uniform of a foreign country or associate with a foreign terrorist organization, has given up their right to be an American citizen."
The bill would expand a 1940s-era law that requires citizens fighting in a military force that is an enemy of the U.S. to renounce their citizenship to include those who are part of a terrorist organization.
The intent of the bill would be to stop terrorists from using their passports to return to the U.S. The State Department would issue a "certificate of loss of citizenship," an aide to Lieberman told Fox News.
It's unlikely the State Department would strip American suspects caught on U.S. soil because of other considerations, like the right to a speedy trial and the suspect appealing the removal of citizenship, the aide said.
Lieberman's bill appears to be gaining bipartisan support. Sen. John McCain, R-Ariz, praised the legislation, and Sen. Chuck Schumer, D-N.Y., reportedly said it "sounds like something I'd support, but I'd have to look at the legislation."
But some lawmakers are skeptical.
"I think that goes too far," Sen. Richard Durbin, D-Ill. told Fox News. "I really believe there are ways to make this country safe without abandoning some of the most fundamental principles. To remove a person's citizenship without some adjudication in my mind is a step too far."
Sen. Lindsey Graham, R-S.C., a military lawyer and often a hawkish ally of Lieberman's on national security expressed concern that the bill would remove the government's ability to prosecute suspects for treason.
"Someone (fitting this scenario) could never get the death penalty unless they were tried for treason," Graham said, adding, "I don't want to take that off the table, the ability to charge someone for treason who's been a citizen who is helping Al Qaeda or the Taliban."
Peter Spiro, a professor at Temple Law School and a citizenship scholar, said he suspects Lieberman's proposal will be dropped well before it becomes law, and would likely be found unconstitutional if it did become law.
"Even the Bush administration didn't go down this road," he said.
The Supreme Court long ago held that Americans can only be stripped of their citizenship where they intend to relinquish it, he said. While at one time, certain acts could supply evidence of such intent, today, the only way individuals lose their citizenship is when they expressly renounce it, he said.
Fox News' Trish Turner and FoxNews.com's Stephen Clark contributed to this report.