261 Current and Former Members of Congress File Supreme Court Amicus Brief Challenging Trump Mail-Voting Executive Order

On September 9, 2026, a bipartisan, bicameral coalition of 261 current and former Members of Congress filed an amicus brief with the U.S. Supreme Court in the case U.S. Postal Service v. California. The brief challenges President Donald Trump's Executive Order 14399 ('Ensuring Citizenship Verification and Integrity in Federal Elections') and a related USPS final rule that impose new restrictions on mail-in voting. The lawmakers argue that the order violates the separation of powers, usurps Congress's Article I authority and states' traditional power over election administration, and threatens to disenfranchise millions of voters ahead of the November 2026 midterms. The filing supports a lower court's preliminary injunction that blocked the USPS rule. This amicus brief is a major congressional response to Trump's executive overreach, escalating the legal challenge to the Supreme Court and highlighting the separation-of-powers conflict.