Related Rule
Canada
Practice Relating to Rule 8. Definition of Military Objectives
Section F. Lines and means of transportation
Canada’s LOAC Manual (1999) considers that “military bases, … ports and airfields; and … military aircraft” are “generally accepted as being military objectives”. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 4-2, § 9(a).
The manual adds that “transportation systems for military supplies; … transportation centres where lines of communication converge; [and] railyards” “depending on the circumstances, may constitute military objectives”. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 4-2, § 11(a), (b) and (c).
Canada’s LOAC Manual (2001) states in its chapter on targeting:
1. The following are generally accepted as being military objectives:
a. military bases, … ports and airfields; and
b. military aircraft …
2. Civilian vessels, aircraft, vehicles and buildings are military objectives if they contain combatants, military equipment or supplies.
3. The following objects, depending on the circumstances, may constitute military objectives:
a. transportation systems for military supplies;
b. transportation centres where lines of communication converge;
c. rail yards. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 407.1–3(a–c).