(A) THE PRINCIPLE OF COMPULSION
Although compulsion is not a ground of restitution in its own right, it is a general principle which underlies a number of specific grounds of restitution, most notably duress. The essence of the principle of compulsion is that it arises where pressure has been placed on the claimant to transfer a benefit to the defendant. Compulsion operates in a similar way to mistake as an explanation of why the receipt of an enrichment by the defendant can be regarded as unjust, namely that the pressure is treated as vitiating the claimant’s intention that the defendant should receive the enrichment. This is because, where the claimant is pressurized into transferring a benefit to the defendant, the claimant’s autonomy has been interfered with to such an extent that he or she cannot be considered to have freely exercised a choice to transfer the benefit to the defendant.
(B) DIFFERENT TYPES OF ENRICHMENT
Although all of the reported cases have concerned claims for the restitution of money paid as a result of compulsion, there is no reason why restitutionary claims cannot be founded on this principle where the claimant has been compelled to transfer non-money benefits to the defendant. Where the claimant has been compelled to transfer goods or to provide services it is still possible to conclude that his or her intention to transfer the benefit has been vitiated as a result of the compulsion. Although it is usually more difficult to establish that the defendant has been enriched by the receipt of goods or services, this is less so where the defendant compelled the claimant to transfer the benefit, simply because the fact of compulsion suggests that the defendant valued the benefit and so he or she will not be able to rely on the defence of subjective devaluation.