The exception is when such reception is „unfair“ or „unjustified“. Both civil and customary legal systems have a legal system that provides remedies to reverse such enrichment. In civil legal systems, unjustified enrichment is often referred to as unjustified enrichment. Its historical foundation of enrichment without reason dates back to the Corpus Iuris Civilis.  While the notion of unjustified enrichment was unknown in classical Roman law, the Roman courts eventually triggered the principle of unjustified enrichment based on two acts of the classical Roman period – the condictio and the actio de rem verso. .