WASHINGTON — California and 22 other Democratic-led states urged the Supreme Court on Monday to block President Trump’s plan to regulate mail ballots through the U.S. Postal Service. The District of Columbia joined the 23 states in urging the Supreme Court to leave in place the lower court order blocking the executive order.

The states filed a 45-page brief with the Supreme Court arguing that implementing new mail ballot regulations this late in the election year would lead to mistakes, such as eligible voters being excluded from federal approval lists. Because of the high risk of errors and the limited window for correcting mistakes, many of the millions of voters who rely on mail voting — especially voters with disabilities and those in rural areas — would likely be denied mail ballots and disenfranchised, the states told the court.

The states argued that the Constitution entrusts states and Congress, not the president, with the responsibility to set rules for federal elections. They noted that Congress has refused to adopt new voting restrictions at Trump’s behest. Trump has insisted that voting by mail leads to fraud, including by allowing noncitizens to vote.

The legal challenge centers on an executive order President Trump issued on March 31, 2026, directing the U.S. Postal Service and the Department of Homeland Security to ensure citizenship verification in federal elections. The executive order required the Department of Homeland Security to compile state-by-state lists of citizens eligible to vote. It also instructs the Department of Homeland Security to send lists of adult U.S. citizens to states at least 60 days before a federal election.

The executive order directed the U.S. Postal Service to use state-specific lists of enrolled voters and prohibited transmitting mail-in or absentee ballots to individuals not on those lists. The USPS shall not transmit mail-in or absentee ballots from any individual unless those individuals have been enrolled on a State-specific list, the order stated. The executive order required states to use tracking barcodes on ballot envelopes. It also directed the U.S. Attorney General to prioritize the investigation and prosecution of state and local officials who issue federal ballots to ineligible individuals.

Trump Solicitor General D. John Sauer sent an emergency appeal to the Supreme Court last week contending that judges in Boston moved too quickly to halt the administration’s new federal restrictions on voting by mail. Sauer argued that judges should stand back for now, even though the midterm elections are only three months away. He argued that the dispute is not yet ripe because the agencies have not yet decided how they will implement the order. Even if the agencies’ implementation plans end up being entirely lawful, there is not enough time to obtain ordinary appellate relief from the injunction in order to carry them out before the November election, especially given that any such plans will need to be implemented well before November given the timing of election procedures concerning voter-roll verification and mail voting, Sauer wrote.

U.S. District Judge Indira Talwani ruled that the federal government could not implement the executive order’s provisions in the 23 challenging states and the District of Columbia before November 3, 2026. Judge Talwani concluded that the challengers’ claims were not ripe for federal elections after November 3, 2026, but were reviewable for the upcoming midterm elections because the order created a direct and immediate dilemma. The U.S. Court of Appeals for the 1st Circuit declined to put Judge Talwani’s order on hold.

The 1st Circuit rejected suggestions that the challengers lacked standing or that the case was not ripe, stating the consequences of the order gave states no practical choice but to respond immediately. The 1st Circuit noted that neither the federal government nor the 12 intervening states defended the legality of the executive order. A group of 12 states, led by Alabama, joined the case to defend the executive order.

The states told the court that the U.S. Postal Service delivered nearly 100 million mail ballots to or from voters in 2024. Roughly 30% of all voters nationwide cast ballots by mail in 2024. The Supreme Court is likely to act in a few days on whether to allow the Trump administration’s plan to proceed pending the adoption of new guidelines. The Supreme Court could rule later this month on the emergency appeal.

Why It Matters

The Supreme Court's decision will determine whether new federal mail ballot regulations take effect before the midterm elections, just three months away. States argue that implementing these rules so late risks disenfranchising millions of voters who rely on mail voting, particularly those with disabilities and in rural areas. The case also tests the constitutional boundary between presidential authority and the traditional role of states and Congress in setting election rules.