Handbook

Restitution of unjust enrichment remains a contentious area of the common law with a vibrant academic and judicial discourse. This is because, in comparison with civilian legal systems, Australia (1987) and England and Wales (1991) were both slow to recognise unjust enrichment as a source of rights and duties within the law of obligations. Since the late 1980s and early 1990s many unjust enrichment claims have been decided in Australia and England, resulting in significant divergences between the two jurisdictions. These divergences remain contentious and a source of debate between appellate courts and legal scholars.

At a high level of generality, a plaintiff in an unjust enrichment case must show that: (i) the defendant was enriched; (ii) the defendant’s enrichment was gained at the plaintiff’s expense; and (iii) the defendant’s enrichment was unjust. The court will then, in turn, (iv) consider whether the defendant has any good defences to the claim. This course is arranged in line with this analytical structure and also considers the convergences and divergences between Australian and English law at each stage of analysis.

The main topics of study are set out below:

• Introduction to unjust enrichment and the remedy of restitution
• Introduction to the elements of an unjust enrichment claim
• Enrichment I (valuing enrichment)
• Enrichment II (at the plaintiff’s expense)
• Unjust Factors I (mistaken conferral of a benefit)
• Unjust Factors II (failure of basis/consideration)
• Unjust Factors III (coercion/duress)
• Unjust Factors IV (necessity)
• Defences (change of position/estoppel/ contract/ passing on)