In the aftermath of the Boston bombing standoff that ended last Friday, lawmakers have changed their tune on whether a drone should ever be used to target an American citizen on U.S. soil.

The use of drones to kill American citizens is not "inherently illegal," as long as that citizen is a "combatant," a constitutional expert told a Senate panel considering the implications of targeted killings Tuesday.

"I think it's not inherently illegal to target American citizens so long as American citizens are also combatants in a relevant war. Sometimes U.S. citizens can be classified as enemy combatants" Ilya Somin, a law professor at George Mason University School of Law, told the Senate Judiciary subcommittee on the Constitution, Civil Rights and Human Rights.

"It's not important [what technology we're using], what matters is we're choosing the right target," he said. "If we're choosing the right target then we should use the appropriate weapons, we'd be wrong to ban specific technology."

That question has become increasingly important as senators such as Ted Cruz and Rand Paul consider the possibility of American citizens being targeted by drones on U.S. soil. In September, 2011, suspected Al-Qaeda operative and U.S. citizen Anwar al-Awlaki was killed by a U.S. drone strike in Yemen.

Last month, Paul spent 13 hours filibustering the confirmation of CIA director John Brennan because he said he was concerned that the United States could eventually target citizens on U.S. soil. Tuesday, Paul changed his tune, telling Fox Business Network that he would have approved of a drone targeting Boston bombing suspect Dzhokhar Tsarnaev.

"I've never argued against any technology being used when you have an imminent threat, an active crime going on," Paul said. "If someone comes out of a liquor store with a weapon and fifty dollars in cash … I don't care if a drone kills him or a policeman kills him."

Even liberal senators, such as Al Franken, have considered the possibility that drones could have been useful in taking down Tsarnaev, who was eventually captured, though he suggested using a drone strike would not be ideal and is "odd for [him] to even consider."

"We had a situation in Boston, a guy holed up in a boat who for all accounts had explosives on him. They did send a robot in to take off tarp," Franken said. "Isn't it possible we could see a situation in which we might want to take that person out in a different way [with drones]?"

Retired Marine Corp. General James Cartwright, who has experience using drones overseas, said he doesn't think using a drone would have been a good idea in Tsarnaev's case.

"Inside the US there are so many other means we can use to approach the situation safely," he said. "If [Tsarnaev's] last act was to stand up and put his hands up in a standoff, to shoot him with a drone is not normally something we'd want to do."

Last month, Attorney General Eric Holder said it is "possible, I suppose, to imagine an extraordinary circumstance in which it would be necessary and appropriate under the Constitution and applicable laws of the United States for the President to authorize the military to use lethal force within the territory of the United States."

Cruz said Tuesday that if a suspected terrorist is a U.S. citizen but does not pose an "imminent threat," they should not be targeted.

"If a United States citizen is on U.S. soil and we have intelligence to suggest that individual is a terrorist involved with al-Qaeda but at that moment poses no imminent threat, if they are sitting on U.S. soil at a cafe in Northern Virginia, should we be allowed to kill that citizen?," he asked. "In my view, the answer to that question should be 'absolutely not.'"