How to control the tech giants—Facebook, Twitter, and YouTube—has continued to raise concerns about both media bias and free speech. They are not covered by the First Amendment because they are not government agencies, but when they have the power to silence a former president or quash reports about Hunter Biden’s depredations before a presidential election, many fair-minded people question whether these shocking actions are lawful.

Now, as in so many other areas of our legal system, Justice Clarence Thomas has provided some important thoughts and distinctions in a concurring opinion. The case is Biden v. Knight First Amendment Institute, in which the Supreme Court considered an appeal from the Second Circuit.

The case itself involved President Trump’s effort to block several Twitter users from interacting with his Twitter account. The Second Circuit held that Twitter was a “public forum” that the president could not close off under the First Amendment. Mr. Trump then appealed to the Supreme Court, which determined after his loss of the presidency the case was moot. For ostensibly unrelated reasons, Twitter then shut down the Mr. Trump’s account. Justice Thomas concurred with the mootness judgment, but—as in other unusual and important cases in the past—took the opportunity to write a concurring opinion that will likely stir some new thinking in the bar and judiciary.

“This petition,” Thomas wrote, “highlights that . . . applying old doctrines to new digital platforms is rarely straightforward.” If the Second Circuit was correct in saying that Twitter is a public or government forum in hosting President Trump, he wondered, how is it that “a private company has unrestricted authority to do away with it”? Clearly, Justice Thomas is suggesting, some deeper thought is necessary here. “Also unprecedented,” he noted, “is the concentrated control of so much speech in the hands of a few private parties.” The Court, he believes, “will soon have no choice but to address how our legal doctrines apply to highly concentrated privately owned information infrastructure such as digital platforms.”

The First Amendment, Thomas points out, is not the only tool available to the government. “Where, as here, private parties control the avenues for speech, our law has typically addressed concerns about stifled speech through other legal doctrines . . . part of the solution may be found in doctrines that limit the right of a private company to exclude.”

Here, he is referring to both U.S. and “British predecessor” laws covering common carriers, “including a general requirement to serve all comers.” Although some scholars have argued that these regulations are only justified where the carrier has market power, others have said the key issue is whether the carrier “holds itself out as open to the public.”

Ever the originalist, Justice Thomas notes that “regulations that might affect speech are valid if they would have been permissible at the time of the founding . . . The long history in this country and England of restricting the exclusion right of common carriers and places of public accommodation may save similar regulations today from triggering heightened scrutiny [under the First Amendment] . . . There is a fair argument that some digital platforms are sufficiently akin to common carriers or places of accommodation to be regulated in this manner.”

What’s more, “network effects entrench these companies.” How else can one explain their “astronomical profit margins? . . . that these companies have no comparable competitors highlights that the industries may have substantial barriers to entry . . . It changes nothing that these platforms are not the sole means for distributing speech or information . . . in assessing whether a company exercises substantial market power, what matters is whether alternatives are comparable.” Finally, “if the aim is to ensure that speech is not smothered, then the more glaring concern must perforce be the dominant digital platforms themselves.”

In just this way, Justice Thomas has often prompted the Court and the bar to consider theories that have not yet gained full acceptance. In Whitman v. American Trucking Assns., a 2001 case in which Justice Scalia found that Congress had not violated the nondelegation doctrine when it gave broad authority to the Environmental Protection Agency, Thomas concurred with the result, but wrote a concurring opinion that said in part:

We have overseen and sanctioned the growth of an administrative system that concentrates the power to make laws and the power to enforce them in the hands of a vast and unaccountable administrative apparatus . . . On a future day, I would be willing to address the question whether our delegation jurisprudence has strayed too far from our founders’ understanding of separation of powers.

In the 2019 Gundy case, Justice Gorsuch wrote a powerful dissent based on the view that legislative delegations to administrative agencies violated the Constitution. He was joined by Chief Justice Roberts and Justice Thomas. Subsequently, both Justices Alito and Kavanaugh signaled agreement to take up the issue in a future case.

Justice Thomas may once again have shown the way to resolving a serious issue in our political system.