On December 4, 1981 President Ronald Reagan signed Executive Order 12333, an Executive Order intended to extend powers and responsibilities of US intelligence agencies and direct the leaders of U.S. federal agencies to co-operate fully with CIA requests for information. This executive order was entitled United States Intelligence Activities.
It was amended by Executive Order 13355: Strengthened Management of the Intelligence Community, on August 27, 2004. On July 30, 2008, President Bush issued Executive Order 13470 amending Executive Order 12333 to strengthen the role of the DNI.
Proscription on assassination
Part 2.11 of this executive order reiterates a proscription on US intelligence agencies sponsoring or carrying out an assassination. It reads:
No person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination.
Previously, EO 11905 (Gerald Ford) had banned political assassinations and EO 12036 (Jimmy Carter) had further banned indirect U.S. involvement in assassinations. As early as 1998, this proscription against assassination was reinterpreted, and relaxed, for targets who are classified by the United States as connected to terrorism.
Hmm this sums it up then.. This explains Saddam Hussein, Osama Bin Laden, benazir Bhutto and now Muammar Gaddafi (and sons Mutassim & Khasim)