In a major setback for Trump in one of his biggest battles with the media, US District Judge Tim Kelly issued his order in a lawsuit that the news organisations filed contesting the ban that the Republican president announced on September 18.
Kelly on Thursday ordered the Trump administration to immediately return the outlets' press passes and blocked officials from enforcing the ban for 14 days.
The judge rejected the government's assertion that the ban was motivated by national security concerns.
"The record lacks factual support for defendants' contention that the revocation of plaintiffs' hard passes will in fact protect national security or that national security will be endangered if the court orders their passes reinstated while this litigation proceeds," he said, adding that Trump himself had stated the ban was due to "alleged lack of truthfulness and negativity" of the outlets' reporting.
The White House and representatives for the outlets did not immediately respond to requests for comment.
Trump had said on social media that the three outlets "shouldn't be able to constantly write or report FICTION and LIES", and Justice Department lawyers had sought to justify the ban on national security grounds.
The three outlets sued Trump and other members of his administration in federal court in Washington on Monday, saying the ban violated the US Constitution's First Amendment protections for free speech and a free press, as well as their due process rights.
They requested a temporary restraining order that would immediately reinstate their White House access while their legal challenge plays out.
The legal battle has unfolded just weeks before the November 3 midterm elections in which Trump's fellow Republicans are fighting to retain control of Congress.
Trump's job approval ratings are at record lows in opinion polls amid concerns over issues such as the Iran war and inflation.
Kelly said at a Wednesday hearing that two federal appeals court precedents made clear that journalists were entitled to due process before their White House press passes could be revoked.
The judge said it did not appear that the White House had given the targeted news outlets a meaningful opportunity to contest the revocation of their access.
In a legal filing on Tuesday, the Justice Department argued that access to the White House was a privilege, not an entitlement, and the president had the authority to suspend access by news organisations.
A coalition of press freedom groups and dozens of news organisations filed a legal brief supporting the three news outlets.
They asserted that "stripping journalists and news outlets of their rights because of perceived editorial viewpoint violates decades of Supreme Court jurisprudence".
The brief was signed by the Reporters Committee for Freedom of the Press, Reuters, the Washington Post and Fox News, among others.
