- Applicable law
This chapter considers more specific statutory and common law rules that may also seem to have the potential to deny, or at least affect, a claim based on proprietary estoppel. It therefore considers the effect of informality, incapacity, ultra vires, and illegality. The chapter focuses in particular on informality, as this is the area of most practical importance. In its interaction with rules as to formality, capacity, vires, or legality, proprietary estoppel is no different from any other legal doctrine: it will not be allowed to operate in such a way as to stultify or undermine the statutory or common law rule. The effect of a particular statutory provision on a proprietary estoppel claim will therefore depend on ‘the nature of the enactment, the purpose of the provision and the social policy behind it’; the same can be said for the impact of a non-statutory rule. The court will also have to consider the conduct of each of A and B and whether it would, overall, be ‘disproportionate’ to deny B’s claim. The precise nature of the claimed estoppel is therefore important.