In the United States, censorship involves the suppression of speech or public communication and raises issues of freedom of speech, which is protected by the First Amendment to the United States Constitution. Interpretation of this fundamental freedom has varied since its enshrinement. Traditionally, the First Amendment was regarded as applying only to the Federal government, leaving the states and local communities free to censor or not. As the applicability of states rights in lawmaking vis-a-vis citizens' national rights began to wane in the wake of the Civil War, censorship by any level of government eventually came under scrutiny, but not without resistance. For example, in recent decades, censorial restraints increased during the 1950s period of widespread anti-communist sentiment, as exemplified by the hearings of the House Committee on Un-American Activities. In Miller v. California (1973), the U.S. Supreme Court found that the First Amendment's freedom of speech does not apply to obscenity, which can, therefore, be censored. While certain forms of hate speech are legal so long as they do not turn to action or incite others to commit illegal acts, more severe forms have led to people or groups being denied marching permits or the Westboro Baptist Church being sued, although the initial adverse ruling against the latter was later overturned on appeal to the U.S. Supreme Court case Snyder v. Phelps.

In the United States, freedom of speech and expression is strongly protected from government restrictions by the First Amendment to the U.S. Constitution, many state constitutions, and state and federal laws. Freedom of speech, also called free speech, means the free and public expression of opinions without censorship, interference and restraint by the government The term "freedom of speech" embedded in the First Amendment encompasses the decision what to say as well as what not to say. The Supreme Court of the United States has recognized several categories of speech that are given lesser or no protection by the First Amendment and has recognized that governments may enact reasonable time, place, or manner restrictions on speech. The First Amendment's constitutional right of free speech, which is applicable to state and local governments under the incorporation doctrine, prevents only government restrictions on speech, not restrictions imposed by private individuals or businesses unless they are acting on behalf of the government. However, It can be restricted by time, place and manner in limited circumstances. Some laws may restrict the ability of private businesses and individuals from restricting the speech of others, such as employment laws that restrict employers' ability to prevent employees from disclosing their salary to coworkers or attempting to organize a labor union.