This is taken from the Thames Valley police website:
The UK's laws can be made in a number of ways:
1) Common law comes from basic ideas of justice. These laws can be hundreds of years old
2) Statutes are laws decided by Parliament. An example is the Human Rights Act (1998) This statute brought the European Convention on Human Rights into UK law.
3) Courts have to decide how laws work in practice. They usually use earlier court decisions as a guide when they do this. These earlier decisions are called 'precedents'.
Local authorities can have laws that apply in their area - these are called bylaws. The UK is a member of the European Union, so European laws and conventions are also part of our law. There are also international laws and conventions on what Governments and other bodies can and can't do.