Is custom the law of the trade

That is to say, custom becomes customary law when it is recognized by the State and made legally binding. Customary law is one of the forms of expression of the legal norms of domestic law

Practice is in fact custom, and industry practice is in fact industry custom. How to understand whether the industry practice has legal effect? This is directly related to the understanding of the formal sense of the source of law. If the industry practice that industry habits belong to the formal sense of the source of law, it has legal effect. In my opinion, there is a difference between the source of law in the substantive sense and the source of law in the formal sense. The source of law in the formal sense refers to the form of law from which the legal norms originate. In other words, the formal source of law refers to the form of expression of legal norms. Formal sources of domestic law, including economic law, including customary law.

Customary law refers to customs that are recognized by the state and are legally binding. That is to say, the custom recognized by the state and given legally binding customary law. Customary law is one of the forms of expression of the legal norms of domestic law. The formal sources of international law, including international economic law, including international customary law. International customary law, is recognized by two or more countries and give legally binding international custom.

That is to say, the international custom recognized by two or more countries and given legally binding international customary law. International customary law is one of the forms of expression of the legal norms of international law.

In short, according to the theory of jurisprudence on the source of law, it should be considered: industry practices recognized by the state and given the legal binding, it has become a formal source of law, with the force of law.

At the same time, we have to realize that, according to the theory of contract law, if the contracting parties to a certain industry practices stipulated in the contract concluded in accordance with the law, including industry practices, including the contract is legally binding on the parties to the contract, the parties to the contract must perform the contract, to comply with the above industry practices; Otherwise, it is not in line with the provisions of the contract law.