National law refers to the laws of a specific nation or state. These laws may be enacted by a government agency or judge-enforced. Entities and professionals use international law in situations that involve relations between multiple countries, while national law focuses on county or state laws within a single nation. Understanding the difference between these two types of law is important for those seeking a career in the legal industry.

Nations usually regulate their governments through a combination of constitutional rules, legislation and unwritten common law. Most have constitutions which establish the basic structure of their government by setting out checks and balances on governmental authority and limiting it. They also list certain rights which are to be protected in a separate section generally known as a bill of rights. Countries which do not have a formal written constitution may still have a set of fundamental laws or rules, for example in England, New Zealand and Canada. These are known as a constitutional constitution or an unwritten constitution.

In some countries, an international treaty or norm automatically becomes part of domestic law, based on a constitutional provision or some other form of automatic incorporation. In others, there is a need to implement such an agreement through additional legislation or executive action. In some cases, a treaty or norm is not implemented at all, either because it has no impact on the domestic law of a State or because a State considers that implementation should await future legislative or other action.