But the fate of Trump's order remains uncertain, as a separate injunction blocking a key part of the plan remains in place.
Republicans are locked in a tight battle to retain control of Congress in the midterms. Restricting mail-in ballots would stand to disproportionately benefit Republicans given that Democratic voters traditionally have been more likely to use mail-in ballots.
Monday's ruling from the Supreme Court's 6-3 conservative majority applied to a June injunction from Boston-based US District Judge Indira Talwani.
A coalition of 23 mostly Democratic-governed states and the District of Columbia had sued to stop the executive order over mail-in ballots. The Supreme Court on Monday said it was too soon for the states to challenge the order but left the door open for them to sue again as the midterm contest approaches.
Trump's executive order, issued in March, directed the Department of Homeland Security to compile and transmit to the states a list of US citizens eligible to vote in each state, and the Justice Department to prioritise investigating and prosecuting state and local election officials who issue ballots to people deemed "not eligible" to vote in federal elections.
Trump's executive order is part of his wider efforts to make fundamental changes in US elections. Trump, who has made false claims of widespread fraud in US elections including his 2020 loss to former Democratic president Joe Biden, has pressed the Republican-controlled Congress to pass a contentious package of voting restrictions called the SAVE America Act.
In Monday's decision, the conservative majority agreed with the Justice Department that the lawsuit challenging Trump's directive was premature and the states did not have the required legal standing at this stage to sue.
The agencies have not yet taken concrete actions that impact the states and so any harm they allege is speculative, the court said. Trump's order itself "does not harm the states," it added.
California Governor Gavin Newsom, a Democrat, said on Monday: "The Supreme Court just let the Trump administration move ahead (for now) with its plan to disenfranchise voters across the country. California will be suing AGAIN to block these Orwellian rules from being implemented."
The White House did not immediately respond to a request for comment. The US Postal Service declined to comment.
Justice Sonia Sotomayor, joined by fellow liberal Justice Elena Kagan, said the states should not have to wait to challenge the order.
"Today's decision does not address whether the president's attempts to interfere with states' administration of the November 2026 elections are lawful," Sotomayor wrote. Justice Ketanji Brown Jackson also wrote a separate dissent.
The states contend their claims are not hypothetical and the administration's "rushed effort to change the rules of mail voting on the eve of the November midterms risks disenfranchising a substantial number of voters".
"This decision is a painful setback, but it will not be the final word," New York Attorney-General Letitia James said in a statement.
"The right to vote is sacred, and no administration should be allowed to put that right in jeopardy by making it harder for eligible voters to cast their ballots."
In her June ruling, Talwani rejected the administration's arguments, finding the lawsuit was not filed too soon and that the states had legal standing because they would face election administration disruption, compliance costs and a credible threat of criminal prosecution.
