1994 to 1995. He served as general counsel of the Senate Judiciary Committee from 1995 to 1996. Academic career (1993–present) Yoo has been a professor at the University of California, Berkeley, School of Law since 1993, where he is Emanuel S. Heller Professor of Law. He has written multiple books on presidential power and the war on terrorism, and many articles in scholarly journals and newspapers. He has held the Fulbright Distinguished Chair in Law at the University of Trento and has been a visiting law professor at the Free University of Amsterdam, the University of Chicago, and Chapman University School of Law. Since 2003, Yoo has also been a visiting scholar at the American Enterprise Institute, a conservative think tank in Washington. He wrote a monthly column, "Closing Arguments", for The Philadelphia Inquirer. He has written academic books including Crisis and Command. Bush administration (2001–2003) Yoo has been principally associated with his work from 2001 to 2003 in the Department of Justice's Office of Legal Counsel (OLC) under Attorney General John Ashcroft during the George W. Bush Administration. Yoo's expansive view of presidential power led to a close relationship with Vice President Dick Cheney's office. He played an important role in developing a legal justification for the Bush administration's policy in the war on terrorism, arguing that prisoner of war status under the Geneva Conventions does not apply to "enemy combatants" captured during the war in Afghanistan and held at the Guantánamo Bay detention camp. Torture memos In what was originally known as the Bybee memo, Yoo asserted that executive authority during wartime allows waterboarding and other forms of torture, which were euphemistically referred to as "enhanced interrogation techniques". Yoo's memos narrowly defined torture and American habeas corpus obligations. They authorized what were called "enhanced interrogation techniques" and were issued to the CIA. Yoo argued in his legal opinion that the president was not bound by the American War Crimes Act of 1996. Yoo's legal opinions were not shared by everyone within the Bush Administration. Secretary of State Colin Powell strongly opposed what he saw as an invalidation of the Geneva Conventions, while U.S. Navy general counsel Alberto Mora campaigned internally against what he saw as the "catastrophically poor legal reasoning" and dangerous extremism of Yoo's opinions. In December 2003, Yoo's memo on permissible interrogation techniques, also known as the Bybee memo, was repudiated as legally unsound by the