In 1981, President Ronald Reagan signed Executive Order 12333, limiting the government’s ability to order assassinations. It’s a long executive order; the most relevant clauses are 2.11 and 2.12:
2.11 Prohibition on Assassination. No person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination.
Clinton, in his interview with Wallace, emphatically stated (regarding Osama bin Laden):
What did I do? I worked hard to try and kill him. I authorized a finding for the CIA to kill him. We contracted with people to kill him. I got closer to killing him than anybody has gotten since.
EO 12333 was subsequently modified and relaxed in 2001, by the Bush administration, following the events of September 11, 2001. However, during Clinton’s presidency, the original order was in effect. It appears reasonably clear that former President Clinton has admitted openly to violating an Executive Order still in force. (Although the theory has been advanced that he was actually lying for political effect.)
As of press time it is not clear what penalties, if any, are prescribed for violation of EO 12333.
(H/T: Protein Wisdom.)
Update: Glenn Reynolds (you know, that lawyer fellow) says “nyet” in a private e-mail, saying that there are no penalties, and that the original EO allows assassination if the President makes a finding, which was what Clinton was referring to.
I don’t see that last part in there; my understanding was that the findings-make-it-OK rule was one of the changes Bush made in 2001. But I could be mistaken.