One law. One plaintiff. Two different challenges.

What is a constitutional challenge?

When lawyers say that a law is “unconstitutional,” they may be describing several different things. The law might be invalid whenever the government enforces it. It might instead be invalid only when applied to particular people, conduct, or circumstances. The distinction between facial and as-applied challenges begins with that difference.

A constitutional lawsuit ordinarily starts with government action. A prosecutor threatens a charge. An agency denies a license. Police conduct a search. A city demands disclosure. A person or organization then argues that the Constitution does not permit the government to take that action under the challenged law.

The plaintiff must identify a constitutional rule, prove the facts needed to establish a violation, and request a remedy. Facial and as-applied challenges are not two separate constitutional rights. They describe how far the claim and requested remedy reach.

What is an as-applied challenge?

An as-applied challenge focuses on a particular operation of a law. The plaintiff accepts—or simply does not ask the court to decide—that the law may be valid elsewhere. The court asks whether enforcing it against this plaintiff, on these facts, would violate the Constitution.

“As applied” does not necessarily mean “after enforcement.” A plaintiff may sometimes sue before the government acts if enforcement is sufficiently threatened and the ordinary requirements of standing and ripeness are met. The phrase describes the claim’s scope, not its timing.

Nor must an as-applied claim concern one uniquely unusual person. A claim can cover a defined category: nonprofit speakers, licensed permit holders, a particular procedure, or property open to the public. It remains as applied when it targets an identifiable operation rather than the entire law.

The advantage is concreteness. Actual facts reduce speculation and allow a court to protect the plaintiff without necessarily interfering with constitutional applications. An as-applied victory ordinarily leaves other enforcement available. An as-applied loss does not prove the law valid in every other setting.

What is a facial challenge?

A facial challenge reaches beyond the plaintiff’s circumstances. It seeks a ruling that a law is invalid throughout a defined universe of applications. Under the demanding general formulation associated with United States v. Salerno, a challenger ordinarily must establish that no set of circumstances exists in which the law would be valid. Later cases express the essential idea by asking whether the law retains a “plainly legitimate sweep.”

The standard reflects judicial restraint. Broad claims can rest on imagined facts, force courts to interpret statutes too early, and prevent elected governments from implementing laws constitutionally. But difficult does not mean forbidden. Facial challenges can succeed when the governing constitutional rule establishes a defect throughout the law’s relevant operation.

The difficult preliminary question is often the denominator: what counts as an application? A court cannot decide whether all—or a substantial share—of a law’s applications are invalid without defining the complete set.

First Amendment overbreadth changes the calculation.

First Amendment overbreadth is a major qualification to the ordinary rule. A speech restriction may be facially invalid when it reaches a substantial amount of protected expression in relation to its legitimate sweep. The challenger need not show that every application is unconstitutional.

The reason is practical. If threatened enforcement causes people to remain silent, many will never become plaintiffs. Case-by-case relief may arrive too late to protect the speech that was never uttered. Overbreadth permits broader review to reduce that chilling effect.

The exception is still demanding. A few marginal unconstitutional examples are insufficient, especially when a law regulates conduct rather than expression. In Moody v. NetChoice, the Court instructed judges to identify the law’s complete range of applications, classify the constitutional and unconstitutional applications, and compare the two sets.

Merits and remedy are separate questions.

Proving a constitutional violation does not automatically determine the judgment. When only some applications are invalid, Ayotte v. Planned Parenthood instructs courts to prefer narrower relief where possible. A court might prohibit the unconstitutional applications or sever a defective provision while leaving the remainder in force.

A separate question concerns who receives protection. A broad holding does not necessarily authorize an injunction protecting everyone. After Trump v. CASA, a federal injunction ordinarily should not extend beyond what is necessary to provide complete relief to the plaintiffs with standing.