Kuwait Court of Cassation principle number 1158

Cause is the legal source conferring the enrichment. The source of the cause may be a contract or the law. The effect of its existence: the enriched person has the right to retain that by which he was enriched, and it bars recourse against him through an action for unjust enrichment. An example of sound reasoning rejecting the appellant's request to order the respondent to pay a sum she received without entitlement, on the basis that she received it in execution of a judicial judgment having the force of res judicata.