The Obama administration asserted on Monday a right to kill Americans overseas who are plotting attacks against the United States, laying out specific details for the first time about a policy that critics argue violates US and international law. US Attorney General Eric Holder said that Americans who have joined Al-Qaeda or its affiliates can be targeted for lethal strikes if there is an imminent threat to the United States and capturing them is not feasible. In a speech to the Northwestern University School of Law, Holder did not refer directly to the CIA drone strike last year that killed Anwar Al-Awlaki, a US-born Muslim cleric who joined Al-Qaeda's Yemen affiliate and directed many attacks. “Any decision to use lethal force against a United States citizen – even one intent on murdering Americans and who has become an operational leader of Al-Qaeda in a foreign land – is among the gravest that government leaders can face,” he said. “The American people can be – and deserve to be – assured that actions taken in their defense are consistent with their values and their laws,” Holder said. US officials have linked Awlaki to several plots against the United States, including the 2009 Christmas Day attempt by a Nigerian man to blow up a US commercial airliner as it arrived in Detroit from Amsterdam with a bomb hidden in his underwear. Holder received a standing ovation when he entered the crowded auditorium but departed to perfunctory applause as some in the audience expressed surprise by his remarks. A question and answer session was canceled, the event organizers said. Civil liberties groups have decried the program as effectively a green light to assassinate Americans without due process in the courts under the US Constitution, a charge that Holder flatly rejected. Court approval for such strikes was unnecessary, he said, adding “the president may use force abroad against a senior operational leader of a foreign terrorist organization with which the United States is at war – even if that individual happens to be a US citizen.” That drew sharp criticism from some in the audience. A third-year law school student, Russell Sherman, called such strikes “assassination” President Barack Obama and his aides have fiercely defended their stand on national security in the face of criticism from Republicans in Congress and on the presidential campaign trail that terrorism suspects are treated too leniently.