The Supreme Court on Monday vacated a ruling that found that former President Trump violated the First Amendment by blocking his critics on Twitter, with the justices dismissing the case as moot.

The court’s move came in an unsigned order. But Justice Clarence Thomas, the court’s most conservative member, wrote separately to voice concern that Trump's removal from Twitter reflected a degree of power in the hands of tech platforms that the court would soon need to address.

The lawsuit arose in 2017 after Trump’s social media account blocked seven people who had tweeted criticism of the president in comment threads linked to his @realDonaldTrump Twitter handle, which has since been banned on the platform.

Lower federal courts found that Trump’s Twitter account, where he often weighed in on official matters, constituted a public forum and that blocking his detractors violated their constitutional free speech protections.

In a 12-page opinion written in concurrence with the court's dismissal of the case, Thomas on Monday expressed alarm over what he referred to as digital platforms’ “concentrated control” of speech. The staunch conservative also said it was inevitable that the court would soon have to take on the issue directly.

“The disparity between Twitter’s control and Mr. Trump’s control is stark, to say the least. Mr. Trump blocked several people from interacting with his messages,” Thomas wrote, noting that Trump had 89 million followers at the time. “Twitter barred Mr. Trump not only from interacting with a few users, but removed him from the entire platform, thus barring all Twitter users from interacting with his messages.”

He later added: "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."

The Trump administration asked the Supreme Court to take up its appeal in the case last August. But following Trump’s electoral loss in November, his administration dropped its request on the eve of President Biden’s inauguration, arguing that the change in administrations would make the case moot.

The Knight First Amendment Institute at Columbia University, which filed the lawsuit on behalf of the seven blocked Twitter users, said it would have preferred the Supreme Court to have left the lower court ruling intact, but added that the litigation had left an important mark.

“We’re pleased with what we were able to accomplish in this litigation — not just forcing President Trump to unblock our clients and dozens of others from his Twitter account, but also establishing a precedent that other courts have invoked to preclude other public officials from silencing their social media critics,” Katie Fallow, an attorney at the Institute, said in a statement.

Updated at 11:21 a.m.