A guide to the developments of 2025 and 2026 that change how the writ and its statutory cousins are used, and to the principles that did not change at all.
The core of mandamus did not change in 2025 or 2026. A petitioner still needs a clear right to relief, a clear duty owed by the respondent, and no other adequate remedy, and a court may still decline the writ in its discretion. What changed is the environment in which those rules are applied. This guide summarizes the developments, each examined in its own article.
The Supreme Court reshaped the remedies around the writ
- Universal injunctions. In Trump v. CASA (2025), the Court held that universal injunctions likely exceed the equitable authority Congress gave the federal courts. Relief now generally runs to the parties, which pushes litigants toward class actions and APA vacatur. See Universal Relief After Trump v. CASA.
- Review bars. In Mullin v. Doe (2026), the Court read the TPS statute's bar on review of "any determination" to foreclose all non-constitutional challenges to TPS terminations. See the case file.
- Removal power. In Trump v. Slaughter (2026), the Court overruled Humphrey's Executor, with consequences for multi-member agencies and for litigants waiting on them. See Agency Quorums, Removal Power and Delay.
- Grant disputes. Orders in 2025 sent challenges to federal grant terminations toward the Court of Federal Claims. See Grant Terminations and the Tucker Act.
The executive branch used the writ, and was ordered by it
The government itself sought mandamus against district-court orders in several prominent cases. In U.S. DOGE Service v. CREW (2025), the Supreme Court vacated a denial of mandamus and ordered discovery narrowed under Cheney; see the DOGE case file. In the District of Columbia, the court of appeals twice granted mandamus in the criminal-contempt proceedings arising from the March 2025 removal flights; see Criminal Contempt, the Executive and the Writ.
Categorical policies tested the delay claim
The largest change for individual petitioners came from category-wide policies: USCIS adjudication holds, a State Department immigrant-visa pause covering 75 countries, and a USCIS memorandum recasting adjustment of status as extraordinary relief. The cases show the limits of an order to decide when the obstacle is a policy rather than a backlog. See the holds, the visa pause, PM-602-0199 and the comparison of § 706(1) and § 706(2).
Procedure moved too
Amendments to the Federal Rules of Civil Procedure took effect on December 1, 2025, including new Rule 16.1 and changes to Rules 16 and 26 on privilege logs. A 43-day lapse in appropriations in late 2025 tested how pending cases proceed without federal funding. And changes at the top of federal agencies made Rule 25(d) substitution a routine question.
State courts
Texas's new Fifteenth Court of Appeals now handles original proceedings in cases involving the State. Courts in Georgia reaffirmed that certifying election results is a ministerial duty enforceable by mandamus, ahead of the November 3, 2026, general election.
What did not change
A court can compel a decision but not dictate its content. The TRAC factors still govern unreasonable-delay claims, and the ministerial–discretionary line still decides whether there is anything to compel. Readers following immigration litigation can track individual rulings in Mandamus Case Law Updates and a review of summer 2026 decisions in the District of Columbia.
Key points
- The three requirements for mandamus and the court's discretion to refuse it are unchanged.
- Supreme Court decisions in 2025–2026 narrowed universal injunctions, broadened a statutory review bar, and overruled Humphrey's Executor.
- The government both sought mandamus against district courts and obtained it.
- Category-wide policies exposed the limits of the delay claim and pushed litigants toward § 706(2) challenges.
- Federal rule amendments took effect on December 1, 2025.
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