Last fall, Justice Clarence Thomas argued that it was time to rein in Section 230 immunity. Now, Justice Thomas is laying out an argument for why companies like Facebook, Twitter and Google should be regulated as utilities.

On Monday, the Supreme Court vacated a lower court ruling in finding that President Trump had acted unconstitutionally by blocking people on Twitter. That case, which the justices deemed moot, hinged on the idea that the @realdonaldtrump account was a public forum run by the president of the United States, and therefore, was constitutionally prohibited from stifling private speech. In his concurrence, Justice Thomas agrees with the decision, but argues that, in fact, Twitter's recent ban of the @realdonaldtrump account suggests that it's platforms themselves, not the government officials on them, that hold all the power.

"As Twitter made clear, the right to cut off speech lies most powerfully in the hands of private digital platforms," Thomas writes. "The extent to which that power matters for purposes of the First Amendment and the extent to which that power could lawfully be modified raise interesting and important questions."

Thomas argues that some digital platforms are "sufficiently akin" to common carriers like telephone companies. "A traditional telephone company laid physical wires to create a network connecting people," Thomas writes. "Digital platforms lay information infrastructure that can be controlled in much the same way."

Thomas argues that while private companies aren't subject to the First Amendment, common carriers are unique to other private businesses in that they do not have the "right to exclude." Thomas suggests that large tech platforms with substantial market power should be bound by the same restrictions. "If the analogy between common carriers and digital platforms is correct, then an answer may arise for dissatisfied platform users who would appreciate not being blocked: laws that restrict the platform's right to exclude," Thomas writes.

Such a restriction would substantially curb tech giants' ability to moderate content, a proposal that both tech giants and those on the left who want to see more aggressive content moderation online would almost certainly reject.

Thomas goes on to describe the sheer scope of Facebook and Google's market power, citing Facebook's roughly 3 billion users and Google's 90% market share in search. "It changes nothing that these platforms are not the sole means for distributing speech or information. A person always could choose to avoid the toll bridge or train and instead swim the Charles River or hike the Oregon Trail," Thomas writes. "But in assessing whether a company exercises substantial market power, what matters is whether the alternatives are comparable. For many of today's digital platforms, nothing is."

Thomas states that in order for an account like @realdonaldtrump to be truly classified as government controlled, "the power of a platform to unilaterally remove a government account" would have to be "reduced."

Thomas acknowledges that it would be up to "a legislature" to impose such a restriction and that the Twitter blocking case before the court didn't offer an opportunity to grapple with those questions. But, he writes, "We will soon have no choice but to address how our legal doctrines apply to highly concentrated, privately owned information infrastructure such as digital platforms."