At issue, was a Second U.S. Circuit Court of Appeals 2019 ruling that upheld a lower court ruling that Trump violated the First Amendment when he used Twitter's block feature to block his critics on Twitter.
Last year, the Justice Department asked the Supreme Court to overturn the 2019 ruling against Trump, arguing it misapplied the First Amendment. But a day before President Joe Biden's inauguration, the Justice Department asked for the case to be dismissed as moot because Trump would be a private citizen.
The Supreme Court announced in an order list Monday without an explanation of the court's reasoning or noted dissents that the judgment was vacated and the case was remanded to the Second Circuit with instructions to dismiss the case as moot.
Justice Clarence Thomas wrote in a concurrence that he agreed with the court's decision "because of the change in presidential administration."
The original lawsuit was filed by the Knight First Amendment Institute at Columbia University in 2017 on behalf of seven people Trump blocked on his @realDonaldTrump twitter based on criticism of his presidency and policies.
Thomas noted separately that the petition "highlights the principle legal difficulty that surrounds digital platforms -- namely, that applying old doctrines to new digital platforms is rarely straightforward."
"Respondents have a point, for example, that some aspects of Mr. Trump's account resemble a constitutionally protected public forum," Thomas added. "But is seems rather odd to say that something is a government forum when a private company has unrestricted authority to do away with it."
The Knight Institute said in a statement Monday that it agreed that the case had become moot, but for a different reason.
"The mootness resulted from Twitter's decision to ban Trump from its platform in response to Trump's repeated violation of its policies," the statement said.
Twitter permanently suspended Trump's account "due to the risk of further incitement of violence" two days after the deadly U.S. Capitol insurrection, following temporary suspension during the rioting, and after months of flagging Trump's content as misleading.