This chapter discusses international sources of law. Conventions and treaties are the primary sources of international law. International law also relies on custom, that is to say informal rules that have been commonly agreed over a period of time. Resolving disputes in international law is very different to resolving domestic disputes, including the fact that in some instances, there is no court that can hear a challenge. The United Nations, particularly its Security Council, has the primary role in upholding international law, meaning that it is often political rather than judicial resolution. In 1972, the United Kingdom joined the (then) European Economic Community (EEC). As part of that process, it agreed to shared sovereignty, meaning that in some areas, European law would take precedence. The United Kingdom has now left the European Union but, as will be seen, its laws will remain an important source of English law for some time.