There are six basic sources of law in the US. Five of them are federal in nature and the sixth is from the state level. The sources are listed below:
1) US Constitution. Constitutional law governs the interpretation of the US Constitution and its statutes.
2) Federal Statutes. Statutory law is the body of written laws that have been passed by the US Congress.
3) Common Law. US common law is also called case law. It is the legal precedents that have been set by judges through legal decisions they make in cases that they oversee.
4) Regulations of Federal Agencies. These include federal agencies like the IRS and FDA.
5) International Treaties. Specifically, treaties that have been approved through a vote in the US Senate.
6) State Laws. State legislatures make state laws that are legitimate as long as they do not conflict with federal law.
Case or Common law is a source of law that originated in England and refers to laws made by judges in the form of precedents. Rulings and decisions made by courts become binding across the jurisdiction’s legal system. The different courts, especially, the lower courts, are in this case required to stand by the previous decision by a higher court, in similar future cases.
Statutory law is a source of law developed by the legislative arm of government. Statutory laws may modify, adopt or abolish whole or parts of Common law. However, the powers of the legislature are controlled by the constitution, to ensure the statutory laws developed by the legislature do not breach constitutional provisions.
Administrative law is a source of law established by different state agencies with the capacity to do so, for instance, regulatory bodies/agencies.
Court rules are a source of law established by the highest court of the land and the legislature, to provide rules for criminal and civil procedures to manage court processes.
The constitution refers to the supreme law of the land. No other laws may be passed or enforced if they contradict or conflict with the Constitutions. However, amendments to the constitution can be achieved depending on the procedural provisions in the constitution. In some countries, amendments must go through a public referendum.
Regional and International treaties are federal sources of law developed to manage international relations.