"In respect of the recent use of deadly force against Osama bin Laden, the United States of America should disclose the supporting facts to allow an assessment in terms of international human rights law standards," Christof Heyns, the expert dealing with extrajudicial, summary or arbitrary executions, and Martin Scheinin, who deals with human rights and counter-terrorism, said in a joint statement.
"For instance it will be particularly important to know if the planning of the mission allowed an effort to capture bin Laden," they said.
The al-Qaida founder was killed at his hideout in Abbottabad, Pakistan, in the predawn hours Monday by U.S. Navy SEALs.
Heyns and Scheinin -- unpaid, independent experts for the U.N. Human Rights Council -- asserted the "norm should be that terrorists be dealt with as criminals, through legal processes of arrest, trial and judicially decided punishment."
Obama administration officials insist the clandestine operation, enacted without the knowledge of Pakistani authorities, complied with all domestic and international law.
"Let me make something very clear: The operation in which Osama bin Laden was killed was lawful," Attorney General Eric Holder told Congress Wednesday. "He was the head of al-Qaida, an organization that conducted the attacks of Sept. 11 (2001). He admitted his involvement."
American University Washington College of Law Professor Kenneth Anderson told ABC News the U.S. government's shifting narrative of the raid -- including whether bin Laden was armed and how much resistance the SEALs encountered in the alleged "firefight" -- has engendered some measure of legitimate international criticism.
"Holder was not direct in stating that of course it was legal to target Osama bin Laden, legal to target with lethal force, legal to target without warning or invitation to surrender," Anderson said. "And that has always been the U.S. legal position.
"The United States actually has firm legal views on these points, which unfortunately, probably for reasons of operational secrecy, the senior leadership hasn't properly communicated," he said.
But many observers say capturing bin Laden would have been a next-to-impossible task.
"From a Navy SEAL perspective, you had to believe that this guy was a walking [improvised explosive device]," Sen. Lindsay Graham, R-S.C., said at a Senate Judiciary Committee hearing Wednesday.