UNJUST ENRICHMENT. — A. i. or without cause occurs whenever someone, without a legally recognized cause, derives some pecuniary gain to the detriment of another, without however having committed a legally illicit act.
In Roman law, in various cases of a. i. the injured party was recognized the right to obtain compensation for the damage up to the amount of the other’s enrichment; these cases were generalized in common law.
The CIC likewise provides for certain cases in which the action for a. i. (actio de in rem verso) is admitted in favor of the injured party (cc. 536, § 4; 1527, § 2, etc.); and it is probable that the norms establishing this should be regarded as particular applications of a general principle of the canonical legal system.
Many current civil legislations regulate only certain cases of a. i., and thus give rise to serious doubts as to the existence in them of a general principle on the matter. Instead, the German civil code, the Swiss code of obligations, and other recent codes regulate the action for a. i. comprehensively. The current Italian civil code has likewise formulated in general terms the principle that “whoever, without just cause, has enriched himself to the detriment of another is bound, up to the amount of the enrichment, to indemnify the latter for the corresponding decrease in his assets”; adding however that “the action for a. i. may not be brought when the injured party can pursue another action to obtain compensation for the harm suffered” (arts. 2041–42).