Moreira v. Ontario Lottery and Gaming Corporation, 2013 ONCA 121 has a helpful analysis of when there is a juridical reason for an enrichment:
 In the first step, a plaintiff is required to show that no juristic reason exists from an established category to deny recovery. The established categories include: a contract, a disposition of law, a donative intent, and other valid common law, equitable or statutory obligations. If there is no juristic reason from an established category, then the plaintiff has made out a prima facie case under this component of the analysis:Garland, at para 44.
 At the second step of the analysis, the defendant can attempt to show that there is another reason to deny recovery. At para. 46 of Garland, the Supreme Court indicated that, at this stage, courts should have regard to two factors: the reasonable expectations of the parties, and public policy considerations. In applying these factors, this stage of the analysis may lead to establishing a new category of juristic reason; it may lead to finding a juristic reason applicable only to the particular circumstances; or it may lead to a conclusion that there was no juristic reason for the enrichment.