Соответствующая норма
Practice Relating to Rule 37. Open Towns and Non-Defended Localities
Section C. Attacks on open towns and non-defended localities
The Report on the Practice of Botswana states that, in general, non-defended localities should not be attacked and cites Article 59 of the 1977 Additional Protocol I. 
Report on the Practice of Botswana, 1998, Chapter 1.8.