In what circumstances will the court order a motion to set aside an agreement that was previously enforceable?

In the Toronto v. CUPE case, the court was dealing with the situation of relitigation: the claimant was asking the court to adjudicate an issue that had already been before a court. In the instant case, the claimant is asking the court to set aside an agreement that the claimant has previously asked the court to enforce.

The principle of approbation and reprobation was articulated in the case of Enquist v. Hass, 1979 CarswellBC 288 (B.C.S.C.): The first [principle] is that of approbation and reprobation, which holds that once a person has received benefits from a course of conduct he may not pursue later an inconsistent course of conduct. Generally, it applies to the alternative remedies such as the acceptance of payment of an award in damages and then the filing of a notice of appeal. Such a person is not permitted “to blow hot and then cold”: see 16 Hals. (4th) 1012, para. 1507.