In the context of American jurisprudence, a facial challenge is a challenge to a statute

Statute

A statute is a formal written enactment of a legislative authority that governs a state, city, or county. Typically, statutes command or prohibit something, or declare policy. The word is often used to distinguish law made by legislative bodies from case law, decided by courts, and regulations...

 in court, in which the plaintiff alleges that the legislation is always, and under all circumstances, unconstitutional, and therefore void. It is contrasted with an as-applied challenge, which alleges that the statute may be, in part, unconstitutional, in redress of specific and particular injury.

A facial challenge to a legislative Act is, of course, the most difficult challenge to mount successfully, since the challenger must establish that no set of circumstances exists under which the Act would be valid. United States v. Salerno

United States v. Salerno

United States v. Salerno, 481 U.S. 739 , was a United States Supreme Court decision. It determined that the "Bail Reform Act of 1984", which permitted the federal courts to detain an arrestee prior to trial if the government could prove that the individual was potentially dangerous to other people...

If a facial challenge is successful, a court will declare the statute in question facially invalid, which has the effect of striking it down entirely. This contrasts with a successful as-applied challenge, which will result in a court narrowing the circumstances in which the statute may constitutionally be applied without striking it down. In some cases—e.g. Gonzales v. Carhart

Gonzales v. Carhart

Gonzales v. Carhart, 550 U.S. 124 , is a United States Supreme Court case that upheld the Partial-Birth Abortion Ban Act of 2003. The case reached the high court after U.S. Attorney General Alberto Gonzales appealed a ruling of the United States Court of Appeals for the Eighth Circuit in favor of...

or Crawford v. Marion County Election Board

Crawford v. Marion County Election Board

Crawford v. Marion County Election Board, 553 U.S. 181 was a United States Supreme Court case holding that an Indiana law requiring voters to provide photo IDs did not violate the Constitution of the United States.-Background:...

, a facial challenge has been rejected with either the court or concurring Justices intimating that the upheld statute might be vulnerable to an as-applied challenge.

In First Amendment

First Amendment to the United States Constitution

The First Amendment to the United States Constitution is part of the Bill of Rights. The amendment prohibits the making of any law respecting an establishment of religion, impeding the free exercise of religion, abridging the freedom of speech, infringing on the freedom of the press, interfering...

 cases, another type of facial challenge is enunciated in the overbreadth doctrine

Overbreadth doctrine

In American jurisprudence, the overbreadth doctrine is primarily concerned with facial challenges to laws under the First Amendment. American courts have recognized several exceptions to the speech protected by the First Amendment , and states therefore have some latitude to regulate unprotected...

. If a statute reaches to include substantial protected conduct and speech in relation to the legitimate reach of the statute, then it is overbroad and thus void on its face.