At a Wednesday hearing of the House national security and foreign affairs subcommittee in Washington, University of Notre Dame Law School professor Mary Ellen O'Connell said that drone use was only legal on sharply defined battlefields - and only when used by the military.
The CIA strikes are "a clear violation of international law," Ms O'Connell stressed.
David Glazier of Loyola University is a former research fellow at the Center for National Security Law, and a pro bono consultant to Human Rights First
But Loyola Law School professor David Glazier, a former navy surface warfare officer, disagreed. Mr Glazier argued that "enemy forces" were legitimate targets anywhere. And he contended that it has historically been considered lawful to conduct limited military operations in countries not directly involved in a conflict.
But Mr Glazier acknowledged that pilots operating the drones from afar could be dragged into the dock in the countries where the attacks are mounted because the CIA drone pilots aren't legally combatants.
According to a conservative analysis by the US New American Foundation think tank, US drone strikes in Pakistan between 2004-10 killed between 830 and 1,210 individuals, of whom around 550 to 850 were "described as militants in reliable press accounts."
UN Special Rapporteur on Extrajudicial Executions Philip Alston has called on the Obama adminstration to clarify the legal justification for the remote-controlled air strikes, observing that they
CIA spokesman George Little insisted on Wednesday that the organisation's counterterror operations are "conducted in strict accordance with the law."