Public Law and Private Law: The Two Branches of the Legal System

Two branches of the legal system

This page is for education, information and intellectual discussion. It explains what each authority says and what each court decided. It does not tell anyone to use these arguments, and it is not legal advice.

That branch or department of law which is concerned with the state in its political or sovereign capacity, including constitutional and administrative law …

Black’s Law Dictionary (2d ed. 1910), “Public law”

As used in contradistinction to public law, the term means all that part of the law which is administered between citizen and citizen, or which is concerned with the definition, regulation, and enforcement of rights in cases where both the person in whom the right inheres and the person upon whom the obligation is incident are private individuals.

Black’s Law Dictionary (2d ed. 1910), “Private law”

The distinction goes back to Roman law, which divided ius publicum (the law of the state) from ius privatum (the law between individuals). Modern legal systems still organize their rules this way.

What falls under each branch

• The public branch: constitutional law, administrative law, criminal law, tax law, and the law of public offices and elections. The government is always one of the parties, and it acts with authority it holds over everyone in its jurisdiction.
• The private branch: contracts, property, torts, trusts, family law, and commercial law such as the Uniform Commercial Code. The parties are private persons or businesses, and obligations usually arise from agreement, ownership or a wrong done to another.
• Mixed areas: consumer protection, employment and securities law use statutes to regulate private relationships. The government may also act as a private party — for example, when it signs a contract or owns property.

Public Law and Private Law as labels on federal statutes

Most laws passed by Congress are public laws. Public laws affect society as a whole. … Private laws affect an individual, family, or small group, and are enacted to assist citizens that have been injured by government programs or who are appealing an executive agency ruling such as deportation.

U.S. Government Publishing Office, “About Public and Private Laws”

Every enacted federal statute is numbered as a Public Law (for example, Pub. L. 97-280) or a Private Law. This labeling is about who the statute affects. It is related to, but not the same as, the academic division described above.

Why the line matters

The two branches use different sources of obligation. Between private persons, most duties arise from consent — a contract, a deed, a trust. In the public branch, duties come from constitutions and statutes enacted by representatives, and they bind people whether or not they agree individually. That difference explains why a person can cancel a private contract under its terms but cannot cancel a criminal statute, a tax or a traffic law.

The branches also use different remedies. A claim between private persons is usually a lawsuit by the injured person for damages or specific performance. A violation of a statute is usually enforced by the government through prosecution, fines or administrative action.

How to check the public law and private law claim yourself

If someone offers you a strategy built on public law and private law, ask for the court decisions that accepted it. In the decisions cited on this page, courts did not accept it. Instead, read the real statute or rule the claim cites, and then read how courts have applied it. Also, look at the cases listed above. They show what happens when people raise the argument in court. For a real dispute, talk to a licensed attorney in your state. You can start with our directory.

Sources and further reading

Official sources used on this page:

• govinfo.gov
• openjurist.org
• thelawdictionary.org

Related reading on Lawtopolis:

• "Everything in Public Is by Contract": Consent, Licenses and Contract Theory
• Contract Law and Consent: How Contracts Form and When They Bind
• Separation of Powers: Legislative, Executive and Judicial Branches
• "The United States Is a Corporation": 28 U.S.C. § 3002(15), 18 U.S.C. § 5 and Merriam's Estate