Both of these articles have a connection to US – Iranian relations. The first, however, goes into some detail on directed assassinations. There’s a long history, some of it considered in this article, on the US connection to assassinations but not much on the actual target assassinations conduct by US forces or agencies after our covert operations in World War II concluded. On the other hand, the country that has perfected the technique of directed assassination, Israel, has conducted scores perhaps hundreds of the operations since their statehood in 1947. A book I can refer you to on these Israeli operations is  “Rise and Kill First- The Secret History of Israel’s Targeted Assassinations” by Ronen Bergman. It is an eye-opening consideration of the subject and leaves the reader in doubt as to the effectiveness of the tactic over time.
I had an opportunity to talk with the Chief Justice of the military Court of Appeals after a presentation he made at the Washington and Lee Law school some years ago. I asked him about the justification in Constitutional law for the directed assassination of an American citizen in Yemen, Anwar Awlaki on September 30, 2011, by a US drone strike. He told me that the elements of proof for such a legal decision required the target, a US citizen, to be giving comfort to or aiding an enemy of the United States during time of war. This is generally the same definition in the Constitution of the crime of treason (less the third element, a requirement that it be testified to by two witnesses). As with all covert operations, the final authority to order a directed assassination lies with the president of the United States. There was an executive order issued by Pres. Ford in 1974 which prohibited the use of assassinations by all departments and agencies of the executive branch. This was an executive order and not a federal statute or a decision by the Supreme Court. As a result, and the wake of September 11, 2001, President Bush rescinded that order in the process is now considered to be lawful.
The US Iran and a No-Win Game
The U.S., Iran and a No-Win Game