UNDUE ENRICHMENT. - Unjust enrichment without cause occurs whenever someone, without a cause recognized by law, derives some patrimonial profit to another's detriment, without however having committed a juridically unlawful act.
In Roman law, in various cases of unjust enrichment the injured party was granted the right to be compensated for the damage within the limits of the other's enrichment; these cases were generalized in common law.
The CIC also provides for certain cases in which the action for unjust enrichment (actio de in rem verso) is allowed in favor of the injured party (cann. 536, § 4; 1527, § 2, etc.); and it is probable that the norms establishing this should be considered as particular applications of a general principle of the canon legal order.
Many civil legislations in force regulate only certain cases of unjust enrichment, and thus give rise to serious doubts as to the existence in them of a general principle on the matter. On the other hand, the German civil code, the Swiss code of obligations, and other recent codes regulate the action for unjust enrichment, considered as a whole. The Italian civil code in force has also formulated in general terms the principle that "whoever, without a just cause, has enriched himself to the detriment of another person is bound, within the limits of the enrichment, to indemnify the latter for the corresponding diminution of patrimony"; adding however that "the action for unjust enrichment cannot be brought when the injured party can exercise another action to be indemnified for the prejudice suffered" (arts. 2041-42).
Bibliography
Pio Ciprotti