The most important relevant treaties, the 1949 Geneva Conventions for the Protection of War Victims, are not formally conditioned on reciprocity. Parties to each Convention “undertake to respect and ensure respect for the present Convention in all circumstances” under Article 1 common to the Conventions. The Vienna Convention On the Law of Treaties, Article 60(5), also recognizes that the general law on material breaches, as a basis for suspending the operation of treaties, does not apply to provisions protecting persons in treaties of a humanitarian character. Yet reciprocity is an implied condition in other rules and obligations including generally the law of armed conflict. It is moreover a critical factor in actual observance of the law of armed conflict. Reciprocity is also explicitly the basis for the doctrine of reprisals. Additionally, a few obligations, such as those contained in the 1925 Geneva Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous, or Other Gases, and of Bacteriological Methods of Warfare, are even formally conditioned on reciprocal adherence.  [emphasis in original]

The UN Resolutions and the Geneva Conventions set forth standards regardless of whether observance is reciprocated. Hence, reciprocity is neither a formal condition precedent qualifying the obligation to observe the Conventions, nor does lack of reciprocity excuse failures to comply. 

Some obligations under the law of armed conflict are reciprocal in that they are binding on the parties only so long as both sides continue to comply with them. A major violation by one side will release the other side from all further duty to abide by that obligation. The concept of reciprocity is not applicable to humanitarian rules of law that protect the victims of armed conflict, that is, those persons protected by the 1949 Geneva Conventions. The decision to consider the United States released from a particular obligation following a major violation by the enemy will be made by the [National Command Authorities]. 

Some obligations under the law of armed conflict are reciprocal in that they are binding on the parties only so long as both sides continue to comply with them. A major violation by one side will release the other side from all further duty to abide by that obligation. The concept of reciprocity is not applicable to humanitarian rules that protect the victims of armed conflict, that is, those persons protected by the 1949 Geneva Conventions. The decision to consider the United States released from a particular obligation following a major violation by the enemy will be made by the president. 

Central Command … forces adhered to … fundamental law of war proscriptions in conducting military operations during Operation Desert Storm through discriminating target selection and careful matching of available forces and weapons systems to selected targets and Iraqi defenses, without regard to Iraqi violations of its law of war obligations toward the civilian population and civilian objects.