When the Named Secretary Leaves Office: Rule 25(d) Substitution

Mandamus cases name officials, and officials change. Rule 25(d) substitutes the successor automatically, which is why a case filed against one Secretary can be decided against another.

A mandamus or APA delay case is brought against officials in their official capacity: the Secretary of Homeland Security, the Director of USCIS, the Secretary of State, a consular officer. Those officials change, sometimes in the middle of a case. In 2026 the Secretary of Homeland Security changed when the Senate confirmed Markwayne Mullin on March 23, 2026, to succeed Kristi Noem. Cases filed against Secretary Noem did not have to be refiled. The reason is Rule 25(d).

What the rule provides

Federal Rule of Civil Procedure 25(d) provides that an action does not abate when a public officer who is a party in an official capacity dies, resigns or otherwise ceases to hold office while the action is pending. The officer's successor is automatically substituted as a party. Later proceedings should be in the successor's name, but a misnomer that does not affect the parties' substantial rights must be disregarded. The court may order substitution at any time, but the absence of an order does not affect the substitution.

The appellate counterpart, Federal Rule of Appellate Procedure 43(c)(2), applies the same principle on appeal, and the Supreme Court's own rules do the same. That is why the Supreme Court decided the TPS cases in June 2026 under the caption Mullin v. Doe, although the challenged terminations had been announced by the previous Secretary.

What it means in practice

• No motion is required. Substitution happens by operation of the rule. Many parties nonetheless file a notice so that the docket and caption are accurate.
• The caption changes. Filings after the change should name the successor. A case filed as "v. Noem" may continue as "v. Mullin" without any change in the claims.
• Service does not have to be repeated. The successor steps into the case as it stands.
• Official title is an alternative. Rule 17(d) allows a public officer sued in an official capacity to be designated by title rather than by name, which avoids the issue for future changes.
• Acting officials. When an office is filled on an acting basis, courts routinely substitute the acting official under the rule.

Where the rule does not help

Rule 25(d) applies only to official-capacity claims. A claim against an official personally, for damages, does not pass to a successor. More importantly for delay cases, substitution does not change who has the power to act. If the official who actually controls a file is someone other than the named defendant, substitution of the named defendant's successor does not cure the defect. Courts dismiss claims against senior officials when the complaint does not show how they cause or could redress the delay, a recurring problem discussed in Naming the Correct Respondent and Suing a Federal Officer for Mandamus.

A drafting checklist

Name each official in an official capacity and identify the office. Explain, for each one, the link between that office and the delayed action. Monitor the offices during the case and file a notice of substitution when a change occurs. A self-represented filer will find captions and service explained step by step in How to File a Writ of Mandamus Pro Se, and the government's usual responses to the choice of defendants are mapped in How the Government Defends Immigration Mandamus Cases.

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