States, the District of Columbia, and voting-rights groups are suing in Massachusetts federal court to block a U.S. Postal Service (USPS) rule implementing Executive Order 14399. They allege that the rule’s new mail-ballot envelope and registration requirements are unconstitutional. A nationwide preliminary injunction keeps the rule from applying to the 2026 midterms after the U.S. Supreme Court denied a stay on September 14, 2026, and the merits remain pending.
Latest development Sep 14, 2026
On September 14, 2026, the U.S. Supreme Court denied, by a 7–2 vote, the government’s emergency application to let the U.S. Postal Service mail-ballot rule take effect for the 2026 midterms. Justice Brett Kavanaugh wrote separately to say the rule might ultimately prove lawful but came too close to the election. The preliminary injunction remains in place, and the merits litigation continues in the district court.
Why it matters
The case will decide whether the executive branch can use U.S. Postal Service rulemaking to impose nationwide mail-voting requirements on states close to a federal election. The merits question of the Postal Service’s statutory authority remains open for future elections and affects state mail-voting programs nationwide.
Background
On March 31, 2026, President Donald Trump signed Executive Order 14399, “Ensuring Citizenship Verification and Integrity in Federal Elections.” The order directed the Department of Homeland Security (DHS) to compile citizenship lists and the United States Postal Service (USPS) to impose new requirements on mail-in ballots. In April 2026, a coalition of states led by California sued in the U.S. District Court for the District of Massachusetts (State of California v. Trump, No. 1:26-cv-11581). The District of Columbia and, later, the Governor of Pennsylvania joined the coalition. The plaintiffs argued that the order exceeded the president’s authority and intruded on the states’ constitutional role in administering elections.
A separate suit, League of Women Voters of Massachusetts v. Trump, No. 1:26-cv-11549, raised similar separation-of-powers, ultra vires, and federalism claims on behalf of voting-rights organizations. After the district court blocked implementation, the government sought emergency relief from the U.S. Supreme Court. On August 24, 2026, in Trump v. California (No. 26A124), the Court voted 6-3 per curiam to lift the injunction. It held that the states lacked standing to challenge the order before USPS had issued a final rule. The Court noted that its ruling did not mean any implementing measure would necessarily be lawful.
USPS issued its final rule, “Ballot Mail for Federal Elections,” on August 21, 2026 (91 Fed. Reg. 54966 (Aug. 26, 2026), to be codified at 39 C.F.R. pt. 111). The rule conditioned USPS’s delivery of mail ballots on states’ compliance with new envelope-design, barcode, and federal-portal registration requirements. Once the rule became final, the states filed a new action (California II, No. 1:26-cv-13917), and the League of Women Voters of Massachusetts amended its complaint. Both cases were again before U.S. District Judge Indira Talwani, who granted a temporary restraining order on August 27, 2026. On September 4, 2026, she converted it into a nationwide preliminary injunction.
Judge Talwani found the rule likely unconstitutional and likely to make disenfranchisement of mail voters “practically inevitable” so close to the November election. The government appealed, and the U.S. Court of Appeals for the First Circuit denied its request for a stay on September 10, 2026. The Solicitor General then renewed an emergency application at the Supreme Court (USPS v. California, No. 26A305), which the Court denied by a 7–2 vote on September 14, 2026. Justice Brett Kavanaugh wrote separately to say the rule might ultimately prove lawful but came too close to the election. The preliminary injunction remains in place through the 2026 midterms, and the merits of the challenges to USPS’s rulemaking authority remain pending in the district court.
Timeline 8 events
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JudgmentSupreme Court denies emergency stay, leaving rule blocked
The Court denied the government’s application in USPS v. California, No. 26A305, by a 7–2 vote. Justice Kavanaugh wrote separately, stating that the rule came too close to the election.
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AppealFirst Circuit denies government’s stay request
A panel of Judges Gustavo A. Gelpí, Julie Rikelman and Seth Aframe held the government had not shown entitlement to a stay of the preliminary injunction.
First Circuit rejects bid to lift injunction blocking USPS rule for mail-in votingFirst Circuit Upholds Block on USPS Mail Ballot Rule
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JudgmentDistrict court enters nationwide preliminary injunction
Judge Talwani found the final rule likely unconstitutional and likely to make voter disenfranchisement “practically inevitable,” blocking its mandatory provisions.
Federal Court Blocks U.S. Postal Service from Interfering with Mail Ballots in November Election
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OrderStates and voting groups sue over final rule and win restraining order
The states filed a new suit and the League of Women Voters of Massachusetts amended its complaint. Judge Talwani granted a temporary restraining order staying key provisions of the rule.
Unlawful USPS Mail Ballot Rule (California v. U.S. Postal Service, D. Mass.)After federal judge blocked new USPS mail ballot restrictions, DOJ goes to SCOTUS
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JudgmentSupreme Court lifts injunction on standing grounds
In Trump v. California, No. 26A124, the Court ruled 6-3 per curiam that the states lacked standing to sue before USPS issued a final rule. The ruling allowed the executive order to proceed for the time being.
26A124 Trump v. California (08/24/2026)Supreme Court allows executive order limiting mail-in ballots to move forward
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OtherUSPS issues final rule restricting mail ballots
USPS finalized “Ballot Mail for Federal Elections,” imposing envelope-design, barcode and federal-portal registration requirements on state mail-voting programs.
USPS releases its final rule affecting mail-in voting for federal elections
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FilingStates and D.C. sue to block Executive Order 14399
A coalition of states led by California and Massachusetts sued in the U.S. District Court for the District of Massachusetts. They challenged the order as unconstitutional before USPS had finalized any rule.
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OtherTrump signs Executive Order 14399 on election citizenship verification
The order directed the Department of Homeland Security (DHS) to compile citizenship lists and directed USPS to develop new mail-ballot handling requirements ahead of the 2026 midterms.
No. _____ In the Supreme Court of the United States (Application and Appendix)
Experimental AI forecast
How it is madeHow will the First Circuit resolve the government’s appeal of the nationwide preliminary injunction against the USPS ballot-mail rule by September 30, 2027?
- First Circuit affirms injunction40%
- Appeal ends without a ruling20%
- Still pending on September 30, 202720%
- First Circuit vacates injunction12%
- First Circuit narrows injunction8%
- Resolves by
- Sep 30, 2027in 12 months
- Record confidence
- Medium
The First Circuit is most likely to affirm the preliminary injunction against the USPS ballot-mail rule by September 30, 2027 (40%). The same panel already found the government had not shown entitlement to a stay, and the Supreme Court declined to intervene by a 7–2 vote.
How it resolves. Resolves on the First Circuit’s public docket and opinions as of September 30, 2027. “Affirms” means the panel or en banc court upholds the preliminary injunction in full. “Vacates” means it reverses or vacates the injunction in full. “Narrows” means it affirms in part and vacates or modifies in part, including scope limits such as ending nationwide application. “Appeal ends without ruling” means the appeal is voluntarily dismissed, dismissed as moot (for example after a final judgment or rescission of the rule), or otherwise closed without a merits decision. “Still pending” applies if none of these has occurred.
Reasoning
Starting point. Federal appeals from preliminary injunctions against agency rules where the circuit court has already denied a stay pending appeal: Federal courts of appeals affirm most preliminary-injunction grants, roughly 60% to 70%, and affirmance rates are higher after a stay denial.
Courts of appeals affirm roughly 60% to 70% of preliminary-injunction grants, and a prior stay denial by the same court signals a likely affirmance. The First Circuit panel denied a stay on September 10, 2026, and the Supreme Court refused a stay on September 14, 2026, which cuts against the government. That lift is tempered because Justice Kavanaugh’s separate writing rested on election timing and suggested the rule might prove lawful, so the merits of USPS’s statutory authority remain open. After the November midterms, the election-proximity rationale fades, which gives the government a better argument for vacatur or narrowing, including limits on nationwide scope. A large share of outcomes fall outside a merits ruling. The district court could reach final judgment first and moot the appeal, or USPS could revise or rescind the rule before 2028, so dismissal or mootness is the leading alternative at 20%. Timing risk also remains, because non-expedited civil appeals can take more than a year, which keeps “still pending” at 20%.
First Circuit panel already denied the government’s stay request · Supreme Court denied stay 7–2 but on election-timing grounds · Post-midterm mootness or district court final judgment could end appeal · Open question of USPS statutory authority over state ballots · Possible challenge to nationwide scope of the injunction
Generated automatically by Claude Opus 5.5 on Sep 26, 2026 from this case’s record on this site, and published without editorial review. The probabilities are the model’s judgment, not measured frequencies, and they are scored publicly as cases resolve. Not legal or investment advice. How the forecasts are made