The ABCs of American Law: What are the sources of American Law?

A general overview of the sources of American law that govern our daily lives.

(State Dept./Doug Thompson depicting U.S. federalism.)

By: Ian L. Courts, Esq.

We’ve all heard the phrase “that’s against the law/ or that’s unlawful!” However, few of us really understand what that prognosticator of legality is saying! (Quite frankly, the speaker does not either.) Moreover, we are inundated by our politicians, news organizations, friends, co-workers, etc., with appeals to the Constitution, arguments concerning this law or that statute — it all seems so daunting! My purpose in writing this brief piece is to provide some foundational light into the sources of law in America — I am not talking about God, Aliens, or even Hammurabi’s code. My focus for this piece is on the political and judicial sources of American law. Let’s dive in!

  1. There is no one American legal system — there are 51+ distinct but interconnected systems!

It can be easy to believe that there is one American legal system and that the laws that govern us in one part of the country govern us all — however, this is not the case. Under the doctrine of federalism, codified in our United States Constitution, the legal power of the United States is shared between the federal government and states! The 10th Amendment of the United States Constitution endows each of the 50 states with “reserved powers,” meaning any power that the federal government does not have outlined in the Constitution — the states reserve! As a matter of fact, our everyday lives are more governed by our state governments than the federal government. This means that federal law governs federal property and federal political spheres such as the U.S. Post Office, Inter-state commerce, treaties, national economic policy, national defense, foreign policy, etc. While states reserve the sovereign power to regulate intrastate commerce, professional licenses, marriage laws, a massive bulk of criminal law, education, and so on.

Accordingly, there are areas where federal law and state law run concurrently, such as regulating criminal law and civil rights. The bulk of the criminal law that governs you and my everyday life is crafted by our state legislatures, not negating the pervasive impact of federal drug crime and cybercrime laws on us! However, where there is a conflict between state law and federal law, under the “Supremacy Clause” of Article VI, Clause 2, the federal law governs — we saw the critical implications for this in the passage of civil rights legislation in the 20th century.

2. The Sources of American Law — constitutions, statutes, and case law!

A. Constitutions

United States Constitution

The foundational source of American law is the United States Constitution. The U.S. Constitution outlines the structure of our federal government and its powers and the powers of our states. Any law that conflicts with the Constitution’s provisions as interpreted by the U.S. Congress and, more importantly, the U.S. Supreme Court is null and void. In a game of cards, the U.S. Constitution is the Ace! However, the U.S. Constitution sets the bare minimum or base of civil rights and constitutional law — state constitutions, statutes, and federal regulations expand those rights.

State Constitutions

Fun fact, many of our state constitutions are older than the U.S. Constitution and influenced the provisions of the U.S. Constitution. State constitutions, in many instances, provide more civil protections for us than the U.S. Constitution. Moreover, state constitutions are the supreme law of the land in their individual states. Like the U.S. Constitution, state supreme courts and state legislatures are the final arbiters and interpreters of state constitutional provisions. State Constitutions, in many ways, more accurately reflect the thinking and philosophy of the people within that state — and are easier to change and amend. Essentially, every law in the state must comply with the U.S. Constitution and your state’s constitutional provisions.

B. Statutory Law

Federal Codes

The United States Code governs various spheres from criminal to trade to treaties, even taxes. The United States Code is compiled of laws passed by the U.S. Congress and signed by the President, federal regulations given by federal departments, and treaties signed by the President and ratified by the Senate. U.S. Code provisions are interpreted by the U.S. Congress, President, and United States Supreme Court; however, the latter’s interpretation governs the day.

State Statutes

Our state legislatures, state administrative agencies, county commissioners, and city ordinances make up a state’s body of statutory law. Most of the laws governing our everyday interpersonal interactions are governed by state statutes crafted by our state legislatures. State statutes specify the ages persons can be married, rules governing wills, zoning laws, education, speeding, and what murder is defined as. As you can see, state statutes play a significant role in our daily lives; unfortunately, many people do not focus on state legislative races — and it shows.

C. Case Law


Common law the collection of judge-made law passed down through the years, reaching back into the early days of Anglo-Saxon customs in England. For the most part, common law has been eclipsed by or codified into modern statutory law. However, many of our courts retain common law judicial doctrines in their jurisprudence.

Federal Courts

Under the power of judicial review outlined in Marbury v. Madison, our federal courts interpret the U.S. Constitution and her provisions and determine if the actions of the President, Congress, and even our state legislatures and state supreme courts align with that interpretation. Federal courts are divided between Article III courts such as the U.S. Supreme Court, the federal circuit courts of appeals, and federal district courts. The federal justices and judges serve for “good behavior” and are tasked with the lofty assignment of judicial review. While Article I courts are crafted and created by Congress and given limited subject matter jurisdiction and serve for a set-term period. Article I courts consist of bankruptcy courts, trade courts, immigration courts, etc. Our federal courts, through their interpretation powers, create, limit, and expand federal law.

State Courts

Similarly, our state courts interpret state constitutional provisions and state statutory law. State courts have the power of judicial review within their jurisdictions to determine the legality of state statutes and Legislative and Executive actions. Moreover, state supreme courts have the power to, and routinely do, expand the rights the U.S. Constitution provides within their jurisprudence. For most legal incidents we may encounter, our state supreme court will be the final arbiter. Many states impose term limits and mandatory retirement ages on state judges, and thus you have more rotation on state courts. Also, the state’s citizens play a more significant part in selecting and or electing state judges.

Now that we have a general understanding of the sources of American law, when we read our news apps, surf Twitter, or debate politics with our family and friends, we are equipped with the tools needed to thoughtfully engage in meaningful discussion. Maybe, we can even ignite a passion for changing the laws that govern us to better all people.

Attorney, Young Black Voice, Law & Politics Observer.