Does the Constitution require Americans to accept Big Tech censorship? The claim is counterintuitive but the logic is clear: If you submit a letter to this newspaper, the editors have no legal obligation to publish it, and a statute requiring them to do so would be struck down as a violation of the Journal’s First Amendment rights. Facebook and Twitter, the argument goes, have the same right not to provide a platform to views they find objectionable.

Big Tech censorship has provoked interest in new civil-rights statutes—state laws that would bar the companies from viewpoint discrimination on their platforms and services. The First Amendment defense of this private censorship arose in a recent federal district court opinion expressing skepticism about a Florida anticensorship statute. It will come up again when other states, such as Texas, consider civil-rights statutes that focus more tightly on viewpoint discrimination.

With the possibility of multiple state statutes barring Big Tech viewpoint discrimination, it will be essential to understand the extent of the tech companies’ freedom of speech. For this, it is important to consider whether they are common carriers.