National law is the law of a country as established by judges, legal scholars and professional institutions (such as the American Law Institute). It includes the rules on how to conduct a court case and what is required from both sides to make a decision. The law of a nation can be based on various factors such as the Constitution, the laws of a state or city, and international treaties.
The national law of a country is generally created and maintained by the courts of that nation, especially the Supreme Court. The Supreme Court is the highest court in the country and it has supreme authority over all other courts. It also has the power to change or repeal laws if needed.
In the United States, the Constitution is the national law. The Constitution sets the basic rules for a nation including freedom of speech, equality before the law, and more. The Constitution is a fundamental part of the American democratic system. The Constitution is so important that a majority cannot change it, except with a constitutional amendment.
Many international treaties do not stipulate how they will be implemented on the domestic level. This is because the treaties do not necessarily affect private parties. However, there are some treaties that do require domestic implementation, such as the International Convention on the Rights of the Child.