FBI Director Robert Mueller on Wednesday said he would have to go back and check with the Department of Justice whether Attorney General Eric Holder's "three criteria" for the targeted killing of Americans also applied to Americans inside the U.S.

Pressed by House lawmakers about a recent speech in which Holder described the legal justification for assassination, Mueller, who was attending a hearing on his agency's budget, did not say without qualification that the three criteria could not be applied inside the U.S.

"I have to go back. Uh, I'm not certain whether that was addressed or not," Mueller said when asked by Rep. Tom Graves, R-Ga., about a distinction between domestic and foreign targeting

Graves followed up asking whether "from a historical perspective," the federal government has "the ability to kill a U.S. citizen on United States soil or just overseas."

"I'm going to defer that to others in the Department of Justice," Mueller replied.

Indeed, Holder's Monday speech at Northwestern University seemed to leave the door open. While Holder speaks of Americans who lead al Qaeda overseas, the implications of the speech seem broad.

"First, the U.S. government has determined, after a thorough and careful review, that the individual poses an imminent threat of violent attack against the United States; second, capture is not feasible; and third, the operation would be conducted in a manner consistent with applicable law of war principles," Holder said.

Holder said the feasibility of capturing a U.S. citizen terrorist is "fact-specific and potentially time-sensitive."

"Given the nature of how terrorists act and where they tend to hide, it may not always be feasible to capture a United States citizen terrorist who presents an imminent threat of violent attack. In that case, our government has the clear authority to defend the United States with lethal force," he said.

Three Americans were killed last year when lethal force was used against American cleric Anwar al-Awlaki. Awlaki is credited with helping plot the foiled Christmas Day bombing of Northwest Flight 253 by Umar Farouk Abdulmutallab and inspiring the Fort Hood shooting. The two others killed -- his son and a cohort who published his online terror magazine "Inspire" -- were considered by the U.S. to be collateral damage.

Asked about Mueller's response, the Justice Department said the answer is "pretty straightforward."

"The legal framework (Holder) laid out applies to U.S. citizens outside of U.S.," said a spokeswoman pulling excerpts from the attorney general's speech.

Holder said the circumstance were legal when it is a case of "an operation using lethal force in a foreign country, targeted against a U.S. citizen who is a senior operational leader of al Qaeda or associated forces, and who is actively engaged in planning to kill Americans.

The circumstances "are sufficient under the Constitution for the United States to use lethal force against a U.S. citizen abroad," Holder added.

However, the attorney general, referencing legal authority in the War on Terror that dates back to the George W. Bush administration, said the Obama administration is not bound to a particular battlefield.

"Neither Congress nor our federal courts has limited the geographic scope of our ability to use force to the current conflict in Afghanistan," he said.

Holder argued in his remarks that it is "simply not accurate" that the president must get permission from a federal court before taking action against a United States citizen terrorist.

"Due process and judicial process are not one and the same, particularly when it comes to national security. The Constitution guarantees due process, not judicial process," he said.

But Jonathan Turley, a law professor at George Washington University, wrote in Foreign Policy magazine on Wednesday that Holder's remarks not only would be seen by the framers of the Constitution as "the very definition of authoritarian power," but were met "not with outcry but muted applause."

"Holder's new definition of 'due process' was perfectly Orwellian," Turley wrote. "What Holder is describing is a model of an imperial presidency that would have made Richard Nixon blush. ...

"Where due process once resided, Holder offered only an assurance that the president would kill citizens with care. While that certainly relieved any concern that Obama would hunt citizens for sport, Holder offered no assurances on how this power would be used in the future beyond the now all-too-familiar 'trust us' approach to civil liberties of this administration," he wrote.