National law, also referred to as domestic law, is the body of rules that exist within a nation (State). These rules can come from decisions made by judges or legislation enacted by a legislature.
Common principles that are shared by different systems of national law may be a source of international law when there is no conventional or customary international law. In other cases, international law is derived from international conventions that are adopted and interpreted by the governments of contracting parties to the convention.
Various nations follow different practices in “internationalizing” treaty norms. These include incorporating the treaty into the legal structure of the state so that its provisions can be implemented by state authorities.
In the United States, for example, international law is incorporated directly into domestic laws by courts and legislatures through statutes and judicial precedent. These laws create private rights, such as a right of action for negligence or to sue the government for torture under international law.
Some international agreements, such as the European Convention on Human Rights, are automatically a part of the domestic law of a ratifying country. However, this is not always the case.
Moreover, there are other international agreements that require further legislation to give effect to the rights set out in them. This is mainly because the agreements are not self-executing.