Règle correspondante
Practice Relating to Rule 6. Civilians’ Loss of Protection from Attack
According to the Report on the Practice of Iraq, civilians lose their protection from attack if they engage in military acts or in acts that directly serve the armed forces and military operations, even without taking up arms against the other party. The report adds, however, that this exception should be interpreted restrictively in order to avoid abuse. 
Report on the Practice of Iraq, 1998, Chapter 1.2.