US Attorney General Eric Holder defended the government’s use of “lethal force” against American citizens abroad as legal and necessary to protect the nation against terror attacks. The speech marked the first time a senior U.S. official has publicly justified in legal terms the drone attacks that are believed to have killed at least three U.S. citizens on foreign soil in recent months, including key Al-Qaeda figure Anwar al-Awlaki. “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,” Holder said in a speech at a law school in Chicago Monday. “In that case, our government has the clear authority to defend the United States with lethal force.” Holder outlined the circumstances under which “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, would be lawful.” Such circumstances included that a thorough review had determined the individual posed “an imminent threat of violent attack against the United States” and that “capture is not feasible.” Third, the “operation would be conducted in a manner consistent with applicable law of war principles,” Holder told the audience at the Northwestern University School of Law. Holder denied the attacks amounted to assassinations or unlawful killings, saying the practice can only take place “in full accordance with the Constitution.” He said, “Our legal authority is not limited to the battlefield in Afghanistan ... We are at war with a stateless enemy, prone to shifting operations from country to country. “Our government has both a responsibility and a right to protect this nation and its people from such threats.” Civil rights groups have cried foul since the September killing of Awlaki in Yemen in a U.S. raid. U.S. citizen Samir Khan was killed in the same September attack, and Awlaki’s U.S.-born teenage son was killed in October in a suspected U.S. airstrike in Yemen. Critics argued it was illegal for the U.S. military to kill an American citizen on the battlefield, following no attempt to indict him. U.S. intelligence officials believed Awlaki was linked to a U.S. army major charged with shooting dead 13 people in 2009 in Fort Hood, Texas, and to a Nigerian student accused of trying to blow up a U.S. airliner on Dec. 25, 2009. The American Civil Liberties Union – which last month filed a lawsuit seeking the release of documents authorizing targeted drone strikes, such as the one on Awlaki – lashed out at Holder’s comments. “Few things are as dangerous to American liberty as the proposition that the government should be able to kill citizens anywhere in the world on the basis of legal standards and evidence that are never submitted to a court,” ACLU National Security Project director Hina Shamsi said in a statement. “Anyone willing to trust President Obama with the power to secretly declare an American citizen an enemy of the state and order his extrajudicial killing should ask whether they would be willing to trust the next president with that dangerous power.”