Peace Palace, Hague
The Hague Regulations, 1907, cover the protection of civilians during wartime. They are rules of customary international law, and as such are also binding on States which are not formally parties to them.
Article 46 states that
Family honour and rights, the lives of persons, and private property, as well as religious convictions and practice, must be respected.
Private property cannot be confiscated.
Article 50 states that
No general penalty, pecuniary or otherwise, shall be inflicted upon the population on account of the acts of individuals for which they cannot be regarded as jointly and severally responsible.
Article 56 states that
The property of municipalities, that of institutions dedicated to religion, charity and education, the arts and sciences, even when State property, shall be treated as private property.
All seizure of, destruction or wilful damage done to institutions of this character, historic monuments, works of art and science, is forbidden, and should be made the subject of legal proceedings.