Соответствующая норма
Practice Relating to Rule 128. Release and Return of Persons Deprived of Their Liberty
The Report on the Practice of Kuwait states: “Kuwait, like the majority of States, considers he may detain POWs [prisoners of war] until the end of military operations, simply in order to neutralise them.” The report states that the opinio juris of Kuwait is that “immediately following the conclusion of hostilities, the parties must engage in negociations, possibly via a neutral intermediary, with a view to obtaining the release and return of all POWs and internees”. The report specifies, however, that spies “may only be released when they have completed their prison sentences”. 
Report on the Practice of Kuwait, 1997, Chapter 5.4.