The First Amendment to the United States Constitution guarantees the right to freedom of speech, religion, assembly, and the press.

Censorship is the government's restriction of speech, often done to suppress dissenting or unpopular views.

The Strict Scrutiny Test is used to determine whether a particular form of speech is protected by the First Amendment. It requires the government to demonstrate a compelling interest in restricting the speech and that the restriction is narrowly tailored to achieve that interest.

In Schenck v. United States, the Supreme Court held that freedom of speech is not absolute and can be restricted in certain circumstances, such as when it poses a clear and present danger to national security.

The Obscenity Doctrine allows the government to restrict speech that is considered to be obscene, lewd, or indecent.

In Brandenburg v. Ohio, the Supreme Court held that the government cannot punish individuals for expressing unpopular or offensive views, unless those views are likely to incite imminent lawless action.

The Clear and Present Danger Doctrine allows the government to restrict speech that is considered to be a threat to national security.

In United States v. Carolene Products Co., the Supreme Court held that the government cannot restrict speech based solely on its content.

The Libel and Slander Doctrine allows the government to restrict speech that is considered to be defamatory or harmful to someone's reputation.

In First National Bank of Boston v. Bellotti, the Supreme Court held that the government cannot restrict speech based on its political viewpoint.

The Fighting Words Doctrine allows the government to restrict speech that is considered to be a direct incitement to imminent lawless action.

In Virginia State Board of Pharmacy v. Virginia Citizens Consumer Council, the Supreme Court held that the government cannot restrict speech based on its commercial content.

The Clear and Present Danger Doctrine allows the government to restrict speech that is considered to be a threat to public safety or order.

In Reno v. American Civil Liberties Union, the Supreme Court held that the government cannot restrict speech based on its artistic or expressive content.