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Canada
Practice Relating to Rule 18. Assessment of the Effects of Attacks
Canada’s LOAC Manual (1999) states:
Commanders, planners and staff officers have … to refrain from launching any attack which may be expected to cause collateral civilian damage which would be excessive in relation to the concrete and direct military advantage anticipated (proportionality test). 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 4-3, § 24.
Canada’s LOAC Manual (2001) states in its chapter on targeting:
1. Under the LOAC commanders, planners and staff officers have the following obligations:
c. to refrain from launching any attack which may be expected to cause collateral civilian damage which would be excessive in relation to the concrete and direct military advantage anticipated (proportionality test). 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 417.1.c.