Related Rule
Canada
Practice Relating to Rule 54. Attacks against Objects Indispensable to the Survival of the Civilian Population
Section B. Attacks against objects used to sustain or support the adverse party
Canada’s LOAC Manual (1999) states:
Objects indispensable to the survival of the civilian population may be attacked if they are used by an adverse party:
a. as sustenance solely for the member[s] of its armed forces; or
b. in direct support of military action, provided that actions against these objects do not leave the civilian population with such inadequate food or water so as to cause its starvation or force its movement. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 4-8, § 80.
Canada’s LOAC Manual (2001) states in its chapter on targeting:
Objects indispensable to the survival of the civilian population may be attacked if they are used by an adverse party:
a. as sustenance solely for the member of its armed forces; or
b. in direct support of military action, provided that actions against these objects do not leave the civilian population with such inadequate food or water so as to cause its starvation or force its movement. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 445.3.