Laws in the United States come from five main sources: the U.S. Constitution, statutes passed by legislatures, regulations issued by executive agencies, decisions written by courts, and ordinances adopted by local governments. Two more — treaties with foreign nations and executive orders issued by the president — carry legal force in specific situations. Each source operates at a different level of authority, and together they produce the layered system that governs everything from federal tax policy to the noise limits on your street.
The Constitution
The U.S. Constitution sits at the top. It defines the structure of the federal government, divides power among three branches, and guarantees individual rights. Every other source of law — federal statutes, agency regulations, state laws, local ordinances — has to be consistent with it, or a court can strike it down.
That hierarchy is spelled out in Article VI’s Supremacy Clause, which declares the Constitution and federal laws made under it “the supreme law of the land” and binds every state judge to them, regardless of what a state’s own constitution or laws might say.1Legal Information Institute. Article VI – U.S. Constitution When a state law conflicts with a valid federal law, the federal law wins.
Each state also has its own constitution governing internal matters. State constitutions sometimes provide broader protections than the federal version, like stronger privacy rights or more detailed protections for workers. But no state constitutional provision can shrink the rights guaranteed by the federal Constitution.
The Constitution itself can change, but only through the deliberately difficult process in Article V: an amendment must be proposed by a two-thirds vote in both chambers of Congress or by a convention called at the request of two-thirds of state legislatures, and then ratified by three-fourths of the states.2National Archives. Article V, U.S. Constitution All 27 existing amendments came through Congress; the convention route has never been used.
Statutes Passed by Legislatures
Most of the written law you encounter day to day comes from legislatures. At the federal level, a member of Congress introduces a bill. Committees study it, debate it, and often revise it before it goes to the full chamber for a vote. If both the House and Senate pass the bill, it goes to the president.3USAGov. How Laws Are Made
The president can sign it into law or veto it. A veto sends the bill back to Congress with the president’s objections. Congress can still enact the bill over a veto, but only if two-thirds of both chambers vote to override.4Legal Information Institute. The Veto Power That high threshold makes overrides rare.
Once signed, federal statutes are organized into the United States Code, arranged across 54 broad titles by subject matter.5Office of the Law Revision Counsel. Detailed Guide to the United States Code Content Title 18 covers federal crimes and criminal procedure, Title 26 covers the tax code, Title 42 covers public health and welfare, and so on down the list. State legislatures follow a similar pattern, maintaining their own organized codes that address areas like family law, property rules, and business licensing.
Statutes are usually written in general terms. That generality is deliberate, but it also means the words on the page rarely answer every specific question a situation can raise. The next two sources exist largely to fill in those gaps.
Regulations Issued by Agencies
Congress often passes statutes that set a broad goal — protect the environment, ensure workplace safety, prevent consumer fraud — and then delegates the detailed rulemaking to a specialized agency. The Environmental Protection Agency, the Securities and Exchange Commission, and the Federal Trade Commission all draw their authority from these enabling statutes, and the rules they issue carry the force of law.
Agencies cannot simply announce new rules. Under the Administrative Procedure Act, an agency must first publish a Notice of Proposed Rulemaking in the Federal Register, describing the proposed rule, citing its legal authority, and inviting public comment.6Office of the Law Revision Counsel. 5 USC 553 – Rule Making Comment periods typically run 30 to 60 days.7Administrative Conference of the United States. Notice-and-Comment Rulemaking After it closes, the agency has to consider every significant issue raised before publishing a final rule.
Finalized federal regulations are compiled in the Code of Federal Regulations, organized into 50 titles covering different areas of oversight.8eCFR. Titles Agencies can impose civil penalties for violations, often thousands of dollars per day for ongoing noncompliance, which gives these regulations real bite.
How much weight courts give an agency’s own reading of its statute recently changed. For decades, judges applied Chevron deference, meaning they generally accepted an agency’s reasonable interpretation of an ambiguous statute. In June 2024, the Supreme Court overruled Chevron in Loper Bright Enterprises v. Raimondo, holding that judges must use their own independent judgment on whether an agency has acted within its statutory authority.9Supreme Court of the United States. Loper Bright Enterprises v. Raimondo Agency regulations may face more rigorous scrutiny going forward, though past decisions made under Chevron were not retroactively overturned.
Court Decisions and Precedent
Courts do more than resolve individual disputes. When a judge issues a written opinion explaining how a rule applies to a specific set of facts, that opinion becomes part of the body of case law. Over time, those decisions build a detailed framework that guides future cases.
The backbone of this system is stare decisis, Latin for “to stand by things decided.” Under this principle, a court generally follows the rulings of higher courts in the same jurisdiction. A federal district court in New York is bound by the Second Circuit Court of Appeals, and all federal courts are bound by the Supreme Court. That vertical structure keeps similar cases from producing wildly different outcomes depending on which judge happens to hear them.
Not every decision carries the same weight. A ruling from a higher court in the same jurisdiction is mandatory authority; lower courts have to follow it. A ruling from a court in a different jurisdiction, or from a court at the same level, is only persuasive — a judge can adopt the reasoning but is not required to. A California state court decision does not bind a Florida state court, though the Florida court might follow it if the analysis is convincing.
One of the most familiar examples of court-made law is Miranda v. Arizona. In that 1966 decision, the Supreme Court held that prosecutors cannot use statements obtained during a custodial interrogation unless the person was informed of the right to remain silent, warned that anything said could be used against them, and told of the right to have an attorney present.10Library of Congress. Miranda and Its Aftermath Those warnings appear in no statute. They came from the Court’s reading of the Fifth Amendment, and they have shaped police procedure ever since.
Local Ordinances
City councils, county boards, and other municipal bodies pass ordinances that regulate life at the community level. Local governments do not have inherent authority. They get it from the state, and the scope of that power depends on which doctrine the state follows.
Under Dillon’s Rule, a local government can exercise only the powers the state has expressly granted, powers fairly implied from that grant, and powers essential to its basic existence. Under home rule, the state gives cities and counties broader autonomy to govern their own affairs without seeking legislative permission on each issue. Most states apply some version of one or both doctrines, and the balance between state and local control varies widely.
Ordinances cover the issues that affect residents on a day-to-day basis: zoning rules that control how land can be used, noise limits, building codes, business licensing, parking regulations, and public safety rules like requiring property owners to clear snow from sidewalks. Violations generally result in fines, with amounts that vary significantly by jurisdiction. Local governments may also hold administrative hearings to resolve disputes over violations.
Treaties and Executive Orders
Two additional sources round out the picture.
The Constitution gives the president the power to negotiate treaties with foreign nations, but a treaty cannot take effect unless two-thirds of the senators present vote to approve it.11Library of Congress. Article II Section 2 – U.S. Constitution Ratified treaties sit alongside the Constitution and federal statutes as part of the “supreme law of the land” under the Supremacy Clause.1Legal Information Institute. Article VI – U.S. Constitution Some treaties are self-executing and become enforceable domestic law the moment they are ratified. Others are non-self-executing and have no effect in U.S. courts until Congress passes implementing legislation.
Executive orders direct how the executive branch operates and how federal agencies carry out their duties. The Constitution does not mention executive orders by name. Their authority flows from Article II, which vests executive power in the president and requires the president to “take Care that the Laws be faithfully executed,” and from powers Congress has specifically delegated by statute. Executive orders with general legal effect must be published in the Federal Register.12Office of the Law Revision Counsel. 44 USC 1505 – Documents To Be Published in Federal Register
Executive orders can carry the practical weight of a statute, but they have real limits. Congress can override one by passing a new law when the order rests on delegated power. Courts can strike one down if the president lacked the authority to issue it or if it violates the Constitution.13Federal Judicial Center. Judicial Review of Executive Orders A future president can also revoke or replace a predecessor’s order, which is why the legal landscape shaped by executive orders can shift noticeably from one administration to the next.
Which Source Wins When They Conflict
Because so many bodies are producing law at once, conflicts are inevitable, and the resolution follows a predictable order. The federal Constitution sits above everything. Federal statutes and ratified treaties come next, and together they override any conflicting state law. State constitutions govern their own states but cannot shrink federal rights. State statutes outrank local ordinances within the state. Agency regulations have the force of law only within the authority the enabling statute gave the agency, and courts can set a regulation aside if the agency exceeded that authority. Court decisions interpreting any of these sources bind the lower courts within the same jurisdiction. Knowing which source produced a rule tells you not only where to look it up but how much weight it carries if something else says the opposite.