Why Do We Have Laws? What Law Does

Last reviewed: October 3, 2026. This article is general information, not legal advice. It explains how law works in the United States; other countries organize their legal systems differently.

It's easy to think of law as a list of things you're not allowed to do. But most of the time law works quietly in the background: it's why your paycheck arrives, why a store has to honor a refund policy, why you can speak your mind about the government, and why a disagreement with your landlord ends up in front of a judge rather than in a fight.

Short answer: we have laws so people can live together safely and fairly. Law sets shared rules for behavior, protects rights and property, gives a peaceful way to settle disputes, and holds everyone to the same rules, including the people in power. That last idea is called the rule of law.

Five things law does

1. Keeps order and safety

Criminal laws set out conduct that society treats as harmful, such as assault, theft and drunk driving, and the penalties for it. Traffic rules, building codes and food safety rules do the same job in a less dramatic way: everyone follows the same rules, so everyone can predict what others will do.

2. Protects rights and freedoms

Law doesn't only limit people; it also protects them, including from the government. The First Amendment says Congress shall make no law abridging "the freedom of speech, or of the press", and the Fifth Amendment says no person shall "be deprived of life, liberty, or property, without due process of law" (Bill of Rights, National Archives). Laws on discrimination, privacy and consumer protection add further rights.

3. Settles disputes peacefully

People will always disagree, about money, property, contracts, accidents and family matters. Law gives them a place to take those disagreements and a fair process for deciding them. In the federal courts' own words, "A federal civil case involves a legal dispute between two or more parties." Courts also encourage parties to settle, and the federal courts "encourage the use of mediation, arbitration, and other forms of alternative dispute resolution" (US Courts, Civil Cases).

4. Makes everyday life predictable

Contracts, property records, business rules and inheritance laws mean you can sign a lease, buy a car, start a business or leave property to your children, and know the arrangement will be respected. Without enforceable rules, every deal would depend on trust alone.

5. Limits power

Under the rule of law, officials are bound by the law too. The federal courts note that "Courts have the responsibility to interpret the Constitution's meaning, as well as the meaning of any laws passed by Congress." If a law conflicts with the Constitution, the Constitution wins. That's what stops a majority, or a government, from simply doing whatever it wants.

Civil law and criminal law

Most legal problems fall into one of two broad groups.

Criminal cases are brought by the government. In federal court, "Only the government initiates a criminal case", and the defendant must be found guilty "beyond a reasonable doubt". Defendants who can't afford a lawyer have the right to a court-appointed one (US Courts, Criminal Cases).
Civil cases are disputes between people or organizations. The person bringing the case generally has to prove it by a "preponderance of the evidence", meaning more likely than not.

The same event can lead to both. A drunk driver who causes a crash can be prosecuted by the state and also sued by the injured person for damages.

Who makes and applies the law

The US has a federal system. The Constitution "creates a federal system of government in which power is shared between the federal government and the state governments" (US Courts, Comparing Federal and State Courts).

Congress passes federal laws; state legislatures pass state laws; cities and counties pass local ordinances.
Government agencies write detailed regulations under the authority those laws give them.
Courts apply the law to real cases and interpret what it means.

Most legal matters people deal with day to day are handled by state law and state courts. According to the federal courts, state courts hear most criminal cases, probate (wills and estates), most contract cases, personal injury cases and family law matters such as marriage, divorce and adoption.

What this means for you

Rules differ by place. Because so much law is made at state and local level, the answer to "is this legal?" often depends on where you are.
Law gives you tools, not just limits. Small claims courts, protective orders, consumer complaints and contracts are all ways law can work for you.
When in doubt, ask. Court self-help centers, legal aid organizations and licensed attorneys can explain how the law applies to your situation.

What is the main purpose of law?

There isn't just one. Law keeps order and safety, protects people's rights and property, gives a peaceful way to settle disputes, and limits what government itself can do. In the US, the Constitution's Preamble lists aims such as to "establish Justice", "insure domestic Tranquility" and "secure the Blessings of Liberty".

What is the rule of law?

The idea that everyone, including people in government, is accountable to the same laws. The US federal courts describe it as a principle under which all persons, institutions and entities are accountable to laws that are publicly promulgated, equally enforced, independently adjudicated and consistent with international human rights principles.

What is the difference between civil and criminal law?

Criminal law deals with conduct treated as an offense against society; only the government brings a criminal case, and guilt must be proved beyond a reasonable doubt. Civil law deals with disputes between people or organizations, such as contracts or injuries; the person bringing the case usually must prove it by a preponderance of the evidence, meaning more likely than not.

Are law and morality the same thing?

No, though they overlap. Many laws reflect shared moral views, like the ban on theft, but law is a set of enforceable rules made through an official process, while ethics and morality are broader. See the difference between ethics and law.

Who makes the laws in the United States?

Federal laws are passed by Congress, state laws by state legislatures, and local rules by cities and counties. Government agencies write regulations under authority given by those laws, and courts interpret all of them, with the Constitution at the top.

Sources

US Constitution, transcript: National Archives
Bill of Rights, transcript: National Archives
Overview - Rule of Law: US Courts
Civil Cases: US Courts
Criminal Cases: US Courts
Comparing Federal and State Courts: US Courts

Why Do We Have Laws? What Law Does in Everyday Life