Promissory estoppel cannot be used to estop a public official from applying a clear statutory provision, or from fulfilling a statutory mandate.

Nunavut v Agnico-Eagle Mines Ltd., 2016 NUCA 02:

[47] The hearing judge did not have the benefit of Robitaille, and did not apply the ratio of Mount Sinai, both cases establishing pivotal considerations that must be brought to bear when determining the availability of promissory estoppel in the public law context. In Robitaille, although dealing with promissory estoppel in a regulatory offence situation, the Supreme Court of Canada clearly held that the doctrine cannot be used to estop a public official from applying a clear statutory provision, or from fulfilling a statutory mandate. The hearing judge erred in law by failing to recognize this clear limitation on the doctrine of promissory estoppel in the public law context, and by applying the doctrine of promissory estoppel in the face of the express legislative provision of s 8(4.1).