Each country recognized by national law has its own national legal system governing contracts. While contract law systems may have similarities, they may differ considerably. As a result, many contracts include a legal choice clause and a jurisdiction clause. These provisions define the laws of the country that governs the treaty and the country or other forum where disputes are settled. If the treaty itself does not provide for explicit agreement on such matters, countries will have rules to define the law applicable to the treaty and jurisdiction over litigation. For example, Member States apply Article 4 of the Rome I Regulation to decide on the legislation applicable to the Treaty and the Brussels I Regulation to decide on jurisdiction. A contract that is implicit in the law is also called a quasi-contract, since it is not, in reality, a contract; Rather, it is a means for the courts to remedy situations in which one party would be unduly enriched if it were not required to compensate the other. Quantum meriduit claims are an example of this. In some circumstances, these terms are used differently.