Payment based on illegal reason is an important legal system of obligation law of continental law system.

不法原因给付制度是大陆法系债法的一项重要法律制度。

Unjust enrichment system began in Roman law. The remodeling and consolidation of Civil Law and modern civil become an important area of the law of obligation.

不当得利制度起始于罗马法，历近代民法与现代民法的重塑与整合，成为债法领域的一项重要制度。