Lex Mercatoria as Substantive Applicable Law of International Sale and Purchase Contracts

This study aims to analyze lex mercatoria as a substantive applicable law international sale and purchase contract. The research method used is a qualitative method. The research results show that international trade activities often lead to disputes between the parties. And the choice of dispute settlement can be made either in court or in arbitration. There are two types of law that apply and are used in international arbitration, namely arbitration procedure law and arbitration substantive law. The substantive law is in the form of a country's national law and/or international conventions related to contracts and lex mercatoria. Lex mercatoria is the law of traders derived from trade usages and general principles of law. CISG can be classified as one of the lex mercatoria because there are principles that generally govern sales and purchase contracts which are referred to as the general principles of international contract law so that the general law principles in this contract are applied as substantive law by arbitrator judges in deciding contract disputes, international sale and purchase in international arbitration.