Is the law of restitution intended to provide an unearned monetary advantage to plaintiffs who have not sustained any loss?

This appeal concerns a claim for restitution by bar owners. The issue in play is whether the law of restitution is intended to provide an unearned monetary advantage to plaintiffs who have not sustained any loss, having recouped monies paid from a third party. In my opinion, the law of restitution is not available to fill the pockets of bar owners who have recouped from their customers a liquor surcharge paid by the bar owners to the Province of New Brunswick. La Forest J. in Air Canada v. British Columbia, 1989 CanLII 95 (SCC), [1989] 1 S.C.R. 1161, at 1202-1203, held that the law of restitution is not intended to provide windfalls to plaintiffs who have suffered no loss. He said: […] the evidence supports that the airlines had passed on to their customers the burden of the tax imposed upon them. The law of restitution is not intended to provide windfalls to plaintiffs who have suffered no loss. Its function is to ensure that where a plaintiff has been deprived of wealth that is either in his possession or would have accrued for his benefit, it is restored to him. The measure of restitutionary recovery is the gain the province made at the airlines’ expense. If the airlines have not shown that they bore the burden of the tax, then they have not made out their claim. What the province received is relevant only in so far as it was received at the airlines’ expense.