Defendants to criminal or civil proceedings will often seek to escape liability by showing that a public authority has acted ultra vires. For example, a person prosecuted for infringing a byelaw or breaking a licence condition may seek to advance the defence that the byelaw or condition is ultra vires the public authority which made or imposed it. Again, a person sued in debt by a public authority may seek to raise the defence that no money is due because the authority acted ultra vires in imposing the charge which it is now suing to recover. Nowadays, too, the European Court of Justice may hold in effect that an Act of Parliament is contrary to Community law and so should not be applied by UK courts. A person prosecuted, say in a magistrates' court, for a criminal offence created by a statute which is or may be contrary to Community law may seek to persuade the justices to “disapply” the statute—virtually, in the case of a post-Accession statute, to treat it as ultra vires the UK Parliament—and so to acquit him.

This article is a study of judicial attitudes to exclusion clauses in contracts for the sale of land. It examines the various devices which the courts have developed in order to limit the effect of such clauses and suggests that one of these devices has emerged as paramount: the principle that a vendor may, in appropriate circumstances, be estopped from relying on a condition by reason of his knowledge or conduct. One form of this estoppel will be shown to be of particular importance. This is the “well-established rule of equity” that a vendor of land cannot rely on a condition of sale, framed in general terms, to cover a specific encumbrance or other defect in title of which the vendor knew or ought to have known, and which he failed to disclose to the purchaser prior to contracting. The culmination of the article is a study of the rationale and precise manner of operation of this rule-which for convenience will be called the “no-disclosure, no-reliance” rule.

Alan Brudner recently observed that a significant tendency within contemporary legal scholarship has been “the movement toward comprehending private law in terms of non-legal ‘perspectives’ that reduce to surface rhetoric the discourse by which private law articulates and understands itself”. This is most obviously true of the economic analysis of law, and not simply in so far as it introduces a vocabulary that is unfamiliar to the lawyer. For the perspective which has informed the most influential currents within that movement is fundamentally aggregative in orientation, so that legal doctrines developed within a bilateral adjudicative framework, focusing on justice between two parties, are inevitably cast in a subordinate and instrumental role. Economic approaches seek to explain the law from a standpoint outside of the law's own framework, and to reveal a deep rationale for particular legal doctrines which would not be transparent to the lawyers and judges who developed those doctrines.

The principle of frustration of contracts, so succinctly stated by Lord Radcliffe in Davis Contractors Ltd. v. Fareham U.D.C., is now well settled and accepted in both Britain and Australia. Its difficulty lies mainly in its application to particular facts, for opinions may sensibly differ as to whether a given contract is frustrated. Of course it can be conceded that some aspects of the doctrine still raise interesting matters of principle, such as the idea that frustration must not be self-induced. But overall the doctrine itself engenders a certain feeling of contentment.