A bipartisan group of 11 influential Senators have sought from the US President Barack Obama "legal justification" for using armed drones or other counter-terrorism operations to kill American citizens.
Eight Democrats and three Republican Senators wrote a letter to Obama, which was released to the press on Monday, ahead of the confirmation hearing of his CIA chief nominee, John Brennan.
"As the Senate considers a number of nominees for senior national security positions, we ask that you ensure that Congress is provided with the secret legal opinions outlining your authority to authorise the killing of Americans in the course of counter-terrorism operations," the Senators wrote.
Prominent among the Senators include Ron Wyden, Mike Lee, Mark Udall, Chuck Grassley, Jeff Merkley, Susan Collins, Dick Durbin, Patrick Leahy, Tom Udall, Mark Begich and Al Franken.
"In our view, if individual Americans choose to take up arms against the United States as part of an opposing fighting force, there will clearly be circumstances in which the President has the authority to use lethal force against those Americans, just as President Lincoln had the authority to direct Union troops to fire upon Confederate forces during the Civil War," the Senators wrote.
"It is vitally important, however, for Congress and the American public to have a full understanding of how the executive branch interprets the limits and boundaries of this authority, so that Congress and the public can decide whether this authority has been properly defined, and whether the President's power to deliberately kill American citizens is subject to appropriate limitations and safeguards," they said.
The Senators wrote that it is a matter of public record that the Obama administration believes the intelligence community has the authority to knowingly use lethal force against Americans in counter-terrorism operations, and senior intelligence officials have indicated that the Justice Department's Office of Legal Counsel has written non-public legal opinions that explain the basis for this authority.
"A number of us have previously asked to see these opinions, but to date they have not been provided to Congress. We ask for your assistance in providing this information to Congress," they said.
"Specifically, we ask that you direct the Justice Department to provide Congress, specifically the Judiciary and Intelligence Committees, with any and all legal opinions that lay out the executive branch's official understanding of the President's authority to deliberately kill American citizens.
"We are not asking for any pre-decisional legal advice and do not believe that providing this information would violate any Constitutional privilege," the Senators wrote.