MANYLaws

Five sources of law

Law in the United States comes from five main sources, ranked in a rough order. The U.S. Constitution is the supreme law of the land, and under its Supremacy Clause, valid federal law overrides conflicting state law. Each state also has its own constitution, which can protect rights more broadly than the federal one but cannot take federal rights away.

• Constitutions create governments, divide their powers and protect individual rights.
• Statutes are laws passed by Congress or a state legislature.
• Regulations are binding rules that agencies write under authority a statute grants them.
• Case law is the body of court decisions interpreting constitutions, statutes and regulations.
• Ordinances are laws passed by cities, counties and towns.

Federal, state and local layers

The Constitution gives Congress specific powers, such as regulating interstate commerce, coining money and setting rules for naturalization, and reserves the rest to the states or the people. That is why most everyday law, including most crimes, contracts, property, family law and professional licensing, is state law, and why rules differ sharply between states.

Cities and counties exercise powers their state grants them, typically covering zoning, local building rules, noise and parking. Layers can also stack: where a state sets a minimum wage above the federal one, employers covered by both laws generally must pay the higher rate.

How a federal bill becomes law

Only a member of Congress can introduce a bill, and bills that raise revenue must start in the House of Representatives. Most bills never make it out of committee.

• A representative or senator introduces the bill, and it is referred to a committee.
• The committee may hold hearings, amend the text in a markup session and report the bill to the full chamber.
• The full chamber debates and votes, and in the Senate, ending debate on most bills takes 60 votes under current rules.
• The other chamber passes the bill, and any differences are worked out until both chambers approve identical text.
• The President signs the bill or vetoes it, and Congress can override a veto with a two-thirds vote in each chamber.
• A bill the President leaves unsigned for 10 days, not counting Sundays, becomes law without a signature if Congress is in session.

How agencies write regulations

Statutes often set goals and leave the details to agencies such as the Environmental Protection Agency, the Department of Labor or the SEC. Under the Administrative Procedure Act, most binding rules go through notice-and-comment rulemaking: the agency publishes a proposed rule in the Federal Register, explains its reasoning and invites public comments for a set period.

Before finalizing, the agency must consider significant comments, and it publishes the final rule in the Federal Register with an explanation of what changed and why. Most final rules take effect at least 30 days after publication and are then added to the Code of Federal Regulations.

A regulation must stay within the authority Congress granted, and courts can set aside one that goes further. Agency guidance documents explain how an agency reads its own rules, but they generally do not carry the force of law.

How courts interpret laws

Statutes rarely answer every question, so courts decide what the words mean in real disputes. Judges start with the text, read it in context and apply long-standing interpretive conventions. Since the Supreme Court’s 2024 decision in Loper Bright Enterprises v. Raimondo, federal courts decide for themselves what an ambiguous statute means instead of deferring to the agency’s reading.

Decisions then become precedent. Lower courts must follow the rulings of higher courts in their system, so a decision by one federal court of appeals binds courts within its circuit but not elsewhere. When circuits disagree, the same federal statute can mean different things in different regions until the Supreme Court, which hears only a small share of the cases brought to it, settles the question.

An appeal generally reviews the trial record for legal errors rather than hearing new witnesses. Each state’s highest court has the final word on that state’s law, and court names can mislead: in New York, the Supreme Court is a trial-level court and the Court of Appeals is the highest.

Where to find the law

Official sources are free and more reliable than summaries. Each new federal law receives a public law number, and its provisions are then organized by subject into the U.S. Code. Always check the date of the version you are reading, because laws change.

• The U.S. Code arranges federal statutes by subject into numbered titles, such as Title 26, the Internal Revenue Code.
• The Code of Federal Regulations arranges federal regulations by subject into 50 titles.
• The Federal Register, published each business day, carries proposed rules, final rules, notices and presidential documents.
• Congress.gov, run by the Library of Congress, tracks federal bills, their status and their text.
• State legislature websites publish state statutes and track pending bills.
• Municipal codes, usually posted online by the local government or a code publisher, collect local ordinances.

How to read a statute

Statutes are written to be precise rather than readable, so go slowly and read the surrounding sections, not just the one a search returns.

• Read the definitions section first, since ordinary words may carry special meanings there.
• Check the effective date, because a law can pass long before it applies, and some provisions phase in or expire.
• Look for later amendments and confirm you have the current version.
• Track exceptions and cross-references, including phrases such as notwithstanding and subject to.
• Notice the verbs: shall usually imposes a duty, while may usually grants discretion.
• Finish with the regulations and court decisions that apply the statute.