The court first defined what types of force could be considered reasonable in the circumstances, the court held that in order for corporal punishment to be considered reasonable it could only be used for corrective purposes against children capable of appreciating it, could only be "transitory and trifling" in nature, and could not be done in a degrading or harmful manner.

The Crown had conceded that the law adversely affected the child's security of person, so the issue was whether the violation offended a principle of fundamental justice.

She examined the meaning of "reasonable under the circumstances" stating that it included only "minor corrective force of a transitory and trifling nature", but it did not include "corporal punishment of children under two or teenagers", or "degrading, inhuman or harmful conduct" such as "discipline by the use of objects", "blows or slaps to the head" or acts of anger.

McLachlin said that the claim hinges on demonstrating the lack of "correspondence between the distinction and the claimant's characteristics or circumstances" (the second contextual factor from the Law v. Canada test).

Section 43 decriminalizes "only minimal force of transient or trivial impact" and to remove such protection would be dangerous as it would criminalize acts such as "placing an unwilling child in a chair for a five-minute 'time-out'" which would risk destroying the family.