Règle correspondante
Practice Relating to Rule 39. Use of Cultural Property for Military Purposes
Sweden’s IHL Manual (1991) points out:
A condition [for their protection under the 1954 Hague Convention for the Protection of Cultural Property] is that none of these cultural values may be used for military purposes. If this should happen, the adversary is no longer obliged to extend protection to these objects … A question of great practical importance is whether the formulation of Additional Protocol admits any possibility of using the object named in Article 53 for military purposes. This does not need to involve such sensational steps as establishing headquarters or ammunitions dumps in museum or churches – it would more normally concern using the objects as observation posts. As Article 53 aims at giving these objects protection equivalent to that of hospitals, the intention has obviously been that no such object shall be used for military purpose of any kind. If such an object should be so used, there is no longer any requirement upon the adversary to respect the safeguard. 
Sweden, International Humanitarian Law in Armed Conflict, with reference to the Swedish Total Defence System, Swedish Ministry of Defence, January 1991, Section, p. 56–58.