Confining and defining proprietary estoppel: the role of unconscionability

Abstract

The use of proprietary estoppel to make or support claims to property is now common. Case-law tells us that the concept of unconscionability is central to a successful claim, but little guidance is provided as to what ‘unconscionability’ means or how it is to be established. It is often assumed rather than explained. This paper argues that unconscionability in fact has a reasonably clear meaning within the law of proprietary estoppel and that it can be used to define and confine proprietary estoppel within reasonably clear boundaries. It seeks to explain that proprietary estoppel is at heart an antidote to a lack of required formality in the creation or transfer of property rights and, consequently, that the proper meaning of unconscionability is linked to these formality requirements. Unconscionability is therefore not a cover for unregulated judicial discretion, nor a loose term to describe a general sense of unfairness, but a concept which can be used to discriminate objectively between valid and invalid estoppel claims.