Customary law

Customary law is the basis of international law and contains the rules on which general principles of law and treaties are based. Almost all states in the world accept the existence of customary law, though there is some dispute as to which laws are contained within it. Laws of war are a typical example of customary law. Laws of war were codified by The Hague Conventions and the Geneva Convention but in fact have been in existence for many thousands of years.

Whether a treaty or customary law should have preference depends on the age of the relevant laws. As both treaty law and customary law are valid sources of international law, it is usually the newer of these laws that will take precedence. It is also possible, though not common, for a treaty to be modified by customary law. Treaties have in fact overwritten much customary law that previously existed, rather like English common law has been overwritten by legislation in many places.

Customary law is created when states consistently implement the relevant law and when there is a legal obligation to practice it. The practice of establishing the customary law is usually only done by the most powerful states, with many international contacts. In order to establish customary law the practice must be common amongst states and must be consistently practiced, the practice need not encompass all states in the same manner, but there must be a sufficient degree of participation, particularly by the states most likely to be affected.

If you would like to obtain legal advice on customary law, Contact Law can put you in touch with a specialist international law solicitor free of charge. So, if you have any questions or would like our help in finding international law solicitors please call us on 0800 1777 162 or complete the web-form above.