Is there international treaty that prohibits killing a leader?

Hi there!

Searches on [ "anti-assassination" treaty ], [ "no assassination"
treaty ] and [ "international treaty" "no assassination" ] did not
turn up any such agreements.  It appears that such policy is up to
individual countries, and even leaders with policies against
assassination can hide behind "plausible deniability", as suggested in
this article, which mentions a statement in a recently declassified
intelligence manual that "No assassination
instructions should ever be written or recorded":

"Operation Condor: Clandestine Inter-American System."
[  http://larcdma.sdsu.edu/humanrights/rr/PLAarticles/mcsherry.html ]

In the United States, there have been several Executive Orders
prohibiting political assassination:

Executive Order 11905: United States Foreign Intelligence Activities 
February 18, 1976 
Pres. Gerald R. Ford 

Executive Order 12036: United States Intelligence Activities 
24 Jan 78 
Pres. James Carter

Executive Order 12333: UNITED STATES INTELLIGENCE ACTIVITIES 
4 December 1981 
Pres. Ronald Reagan 

...the text of which, in each case, read:

"Prohibition of Assassination. No employee of the United States 
Government shall engage in, or conspire to engage in, political 
assassination."

(Texts collected in the article "Assassination to be Legalized by
House Bil in process")
[ http://www.indymedia.org/front.php3?article_id=19541 ]

As mentioned in the above article, the ``Terrorist Elimination Act of
2001'' {which is still in committee) seeks to nullify those Executive
Orders and effectively legalize political assassination.

"H.R. 19--A bill to nullify the effect of certain provisions of
various Executive orders"
[ http://frwebgate.access.gpo.gov/cgi-bin/useftp.cgi?IPaddress=162.140.64.21&filename=h19ih.txt&directory=/diskb/wais/data/107_cong_bills
]

Hope this helps!

Best regards, 

missy-ga

It could be argued that the Geneva Convention implicitly prohibits
assassinations, since it aims to prevent "wilful killing" that is "not
justified by military necessity."  If you perform the following
search, you'll come across a number of articles that make that
interpretation.

Google search:
geneva convention "wilful killing"

I think the answer above is a bit too cursory a review of
international law.

Basically, international law comes from two sources -- treaty and
custom.  Treaties are binding agreements between two or more states
(countries).  Custom (also called jus cogens, from the Latin for
customary law) is the accepted practice of states, and long-standing
custom has full force of law in international venues.  For example, it
is accepted custom that treaties must be honored.  Some issues are
covered by both treaty and custom, such as the treatment of diplomats.
 Ancient custom prohibits hurting foreign diplomats, and a treaty --
"The Convention on the Prevention and Punishment of Crimes Against
Internationally Protected Persons" -- does the same.

Worth noting is that this same treaty (online at:
http://www.unog.ch/archives/safety1.htm) protects heads of state as
well, which I presume is what is meant by "leader" in the question. 
(More on the treaty is here:
http://untreaty.un.org/English/Terrorism.asp).  The United States is a
party to this convention, making it a breach of international law for
the U.S. to violate it.  Violations include killing a protected
person, trying to do so, or threatening to do so.

Beyond this treaty, various treaty law and customary law prevents
states from killing nationals of another state, which clearly includes
the leaders of foreign states.

If your question referred to actions by individuals (rather than
governments), other treaties would apply.  If, for example, an
American citizen killed a foreign leader, the U.S. might be required
to turn the killer over to the foreign nation for trial and
punishment.  Various human rights treaties might cover such a murder
as well.