Related Rule
United States of America
Practice Relating to Rule 22. The Principle of Precautions against the Effects of Attacks
Section B. Feasibility of precautions against the effects of attacks
At the CDDH, the United States stated:
The word “feasible” when used in draft Protocol I, for example in Articles 50 and 51 [now Articles 57 and 58], refers to that which is practicable or practically possible, taking into account all circumstances at the time, including those relevant to the success of military operations. 
United States, Statement at the CDDH, Official Records, Vol. VI, CDDH/SR.42, 27 May 1977, p. 241.