Lawful combatant is the general term from the Geneva Conventions, where an individual, adjudicated by a "competent tribunal" if necessary, qualifies for prisoner of war status. The critical criteria for lawful combatant status are, according to the Third Geneva Convention:[1]
Under some conditions, the Conventions recognize temporary exceptions to these rules. For example, if there is a "spontaneous uprising" against a surprise invasion of a country, it may be acceptable if they are imprecise on the distinctive insignia, as long as it is their clear intent to put themselves under lawful command, and follow the laws and customs of war.
In the 1874 Franco-Prussian War, the Germans called French resisters francs-tireurs, and unsuccessfully argued for their banning in the 1899 Hague Convention. That convention did establish the four criteria of the Geneva Convention Common Article, but did not stipulate "shooting on sight" or any specific handling other than denial of prisoner of war status. [2]
The George W. Bush Administration used the term enemy combatant or "unlawful combatant" for members of al-Qaeda and certain members of the Taliban, but the Obama Administration has stated its preference simply to speak of "lawful combatants", and people who do not meet the standard of lawful combatants.[3]