The First Amendment to the United States Constitution provides that Congress shall make no law abridging (curtailing) the freedom of speech. Thus, free speech is only protected by the U.S. Constitution when it is the government that seeks to limit free speech. The First Amendment is inapplicable when a nongovernmental person or entity—such as a private business—seeks to limit free speech.

And some types of speech are afforded more protection than others. For example, commercial speech—speech that proposes a commercial transaction—is entitled to First Amendment protection, but less protection than political speech.

In the 1980 case Central Hudson Gas & Electric Corp. v. Public Service Commission, the U.S. Supreme Court developed a four-part test to determine whether commercial speech regulation violates the First Amendment:

1. Whether the commercial speech concerns a lawful activity and is not misleading;

2. Whether the government interest asserted to justify the regulation is "substantial";

3. Whether the regulation "directly advances" that government interest;

4. Whether the regulation is no more extensive than necessary to serve that interest.

In South Carolina, as in all states, the First Amendment to the United States Constitution protects individuals from government actions that would abridge their freedom of speech. This means that the state government, as well as local governments within South Carolina, cannot enact laws or regulations that unduly restrict speech without meeting certain legal standards. However, the First Amendment does not apply to private entities, such as businesses or individuals, when they seek to limit speech on their private property or within their private organizations. Commercial speech, which includes advertising or other speech proposing a commercial transaction, is protected under the First Amendment but to a lesser degree than political or other forms of expression. The Central Hudson Gas & Electric Corp. v. Public Service Commission case provides a four-part test for assessing the constitutionality of commercial speech regulations. South Carolina, like other states, must adhere to this test when enacting laws that affect commercial speech, ensuring that such regulations are justified by a substantial government interest, directly advance that interest, and are not more extensive than necessary.