In a unanimous, pragmatic opinion, the U.S. Supreme Court just drew a roadmap allowing public officials to block users on social media.

Faced with the argument that getting blocked violated a user’s free speech rights, the court held that the First Amendment only bars blocking by public officials who use social media to exercise government authority.

Justice Amy Coney Barrett wrote the sole opinion for the court, which deftly transformed a complex, potentially divisive issue into a simple doctrinal question. Instead of diving into the tricky issue of whose free speech is implicated in social-media blocking — that of the account holder, the person blocked, or even the platform itself — the court instead narrowed the question to whether the public official is engaged in "state action.”

In U.S. constitutional law, state action is a kind of magical talisman, an on-off switch that either triggers the Constitution or takes it off the table. Basically, if the courts think the government is acting in a given situation, then the Constitution applies and limits what the government can do. If, however, the action comes from a private citizen, the Constitution doesn’t apply.

In the context of a public official blocking someone on social media, the court ruled that the Constitution isn’t triggered unless the official is acting as the state. To determine whether that’s happening, the court set two conditions, both of which must be met. The official must have the authority to speak on behalf of the government on the account; and the official must also "purport” to speak on behalf of the government — that is, present their words on the account as official statements.

This clear two-part rule telegraphs to public officials exactly how to avoid getting sued for blocking: All they have to do is say on their accounts that they are speaking for themselves, not officially. Sharing official information or announcements won’t turn the account into state action, the court said, as long as the information is "otherwise available.” This condition is easy to meet. For example, even when former President Donald Trump seemed to be issuing executive decisions by Twitter, those announcements were also usually available on the White House website within minutes.

In other words, the court’s test is designed more to enable public officials to block others than to stop them from doing so. The court emphasized that "officials too have the right to speak about public affairs in their personal capacities” — that is, to speak on their own social media accounts. It added that, "lest any official lose that right, it is crucial for (a) plaintiff to show that the official is purporting to exercise state authority in specific posts.”

This concern for the rights of the public officials is especially noteworthy because you might not automatically think that public officials’ own free-speech rights would be endangered by stopping them from blocking others. The court, however, seemed to imply by its language that blocking is itself a form of speech for social media users.

The decision should reduce the frequency of litigation over blocking. But it won’t eliminate it altogether. The court acknowledged that there will still be fact-specific details to be worked out. It said that an account labeled as the official account of a city, for example, or that "is passed down to whomever occupies a particular office,” would presumptively exercise state action.

The court also left open the possibility that specific statements on an account might count as state action while others might be personal. When blocking is page-wide, the opinion said, rather than post-by-post, "a court would have to consider whether (the official) had engaged in state action with respect to any post on which (another user) wished to comment.” That’s a recipe for confusion rather than clarity.

The bottom line, however, is that in its first foray this term into creating First Amendment rules for social media, with two more to come, the court did well, exercising caution and common sense. If the court continues in this vein, the justices could start the long, slow process of rebuilding some legitimacy in an area of great importance to the future of democracy.

Noah Feldman is a Bloomberg Opinion columnist. A professor of law at Harvard University, he is author, most recently, of "The Broken Constitution: Lincoln, Slavery and the Refounding of America.”