Rule 24.Intervention

Last amended December 1, 2007 · Last verified June 30, 2026

In one sentenceRule 24 lets a nonparty join an existing case: intervention of right is available to one with a protectable interest the case may impair that no party adequately represents, while permissive intervention is allowed when a claim or defense shares a common question.

Full Text of Rule 24

Text sizeJump to: (a) (b) (c)

(a) Intervention of Right. On timely motion, the court must permit anyone to intervene who:

(1) is given an unconditional right to intervene by a federal statute; or

(2) claims an interest relating to the property or transaction that is the subject of the action, and is so situated that disposing of the action may as a practical matter impair or impede the movant's ability to protect its interest, unless existing parties adequately represent that interest.

(b) Permissive Intervention.

(1) In General. On timely motion, the court may permit anyone to intervene who:

(A) is given a conditional right to intervene by a federal statute; or

(B) has a claim or defense that shares with the main action a common question of law or fact.

(2) By a Government Officer or Agency. On timely motion, the court may permit a federal or state governmental officer or agency to intervene if a party's claim or defense is based on:

(A) a statute or executive order administered by the officer or agency; or

(B) any regulation, order, requirement, or agreement issued or made under the statute or executive order.

(3) Delay or Prejudice. In exercising its discretion, the court must consider whether the intervention will unduly delay or prejudice the adjudication of the original parties' rights.

(c) Notice and Pleading Required. A motion to intervene must be served on the parties as provided in Rule 5. The motion must state the grounds for intervention and be accompanied by a pleading that sets out the claim or defense for which intervention is sought.

End

Amendment History

(Amended December 27, 1946, effective March 19, 1948; December 29, 1948, effective October 20, 1949; January 21, 1963, effective July 1, 1963; February 28, 1966, effective July 1, 1966; March 2, 1987, effective August 1, 1987; April 30, 1991, effective December 1, 1991; April 12, 2006, effective December 1, 2006; April 30, 2007, effective December 1, 2007.)

Plain-English Summary

Rule 24 is how an outsider gets into a lawsuit. There are two paths. Intervention of right must be granted, on a timely motion, to anyone given an unconditional right to intervene by statute, or who claims an interest in the subject of the action that the case may, as a practical matter, impair — unless an existing party already adequately represents that interest.

Permissive intervention is discretionary: the court may allow it for someone with a conditional statutory right, or whose claim or defense shares a common question of law or fact with the main action, weighing whether intervention would unduly delay or prejudice the original parties. A motion to intervene must be timely, served on the parties, and accompanied by a pleading setting out the claim or defense. The rule also addresses intervention by a government officer when a statute or regulation is challenged.

Frequently Asked Questions

What is intervention of right?

The right of a nonparty to join a case — on a timely motion — when a statute grants it or when the person has an interest the case may impair that no current party adequately represents (Rule 24(a)).

How does someone join a lawsuit they are not part of?

By moving to intervene under Rule 24, either as of right or with the court’s permission, with a timely motion served on the parties and a pleading stating the claim or defense.

Source & verification. The rule text and amendment history are reproduced verbatim from the official Federal Rules of Civil Procedure (Fed. R. Civ. P. 24), a public-domain work of the U.S. Government. Prescribed by the United States Supreme Court under the Rules Enabling Act. The plain-English summary is original and written by us. Last verified June 30, 2026. · Official source

Also known as: FRCP 24Fed. R. Civ. P. 24interventionintervention of rightpermissive intervention