The Obama administration's use of drone strikes is under heightened scrutiny after the country learned that the federal government considers it legal to use drones to kill Americans overseas if an informed, high-level official believes the citizen poses an imminent threat, CBN News reports. An unclassified Justice Department memo, leaked this week, shows that no clear evidence is needed. The country also learned this week that America launches drones from a secret base in Saudi Arabia, and since Obama took office in 2009, the use of drones has grown 700 percent. Human rights and civil liberties groups have protested the process for targeting terror suspects, especially U.S. citizens. "That justifies essentially a claim that the Executive Branch can be judge, jury and executioner," said Hina Shamsi, director of the American Civil Liberties Union's National Security Project. The controversy is illustrated in the case of Anwar al-Awlaki -- an American citizen but also a top al Qaeda leader linked to several terror attacks -- who was killed in an unmanned U.S. drone strike in Yemen in 2011. Many in the military believe drone strikes will continue to grow in importance but that more thoughtful debate about their use is needed.