---
title: "Intervention (Rule 24)"
type: Legal Rule
source: https://casebriefly.com/legal-rules/intervention-rule-24
---

# Intervention (Rule 24)

Federal Rule 24 allows nonparties to join an existing lawsuit either as of right when their interests may be impaired or permissively when their claims share common questions with the pending action.

## Definition

Federal Rule of Civil Procedure 24 governs intervention, the process by which a nonparty seeks to become a party to an existing lawsuit. Intervention may be either of right under Rule 24(a) or permissive under Rule 24(b). The rule reflects the recognition that litigation may affect the interests of persons who are not original parties, and fairness may require that they be allowed to participate.

Intervention of right under Rule 24(a)(2) requires four elements: (1) the application must be timely; (2) the applicant must claim an interest relating to the property or transaction that is the subject of the action; (3) the applicant must be so situated that disposing of the action may as a practical matter impair or impede the applicant's ability to protect that interest; and (4) existing parties must not adequately represent the applicant's interest. If all four elements are met, the court must allow intervention. The interest requirement has been interpreted broadly by most circuits, encompassing significant protectable interests beyond mere property rights.

Permissive intervention under Rule 24(b) is discretionary and available when the applicant's claim or defense shares a common question of law or fact with the main action, or when a federal statute confers a conditional right to intervene. The court considers whether intervention will unduly delay or prejudice the adjudication of the original parties' rights. Subject matter jurisdiction must be independently established for permissive intervention, though intervenors of right may rely on supplemental jurisdiction in some circumstances.

## Elements

- Intervention of right: timely application, claimed interest in the subject of the action, potential impairment of that interest, and inadequate representation by existing parties
- Permissive intervention: common question of law or fact with the pending action, no undue delay or prejudice
- Timeliness is required for both types of intervention
- Intervention of right is mandatory if all four elements are met
- Permissive intervention is within the court's discretion
- Subject matter jurisdiction must be independently established for permissive intervenors

## Key Case

Trbovich v. United Mine Workers of America, 404 U.S. 528 (1972)

## Landmark Cases

| Name | Citation | Significance |
| --- | --- | --- |
| Trbovich v. United Mine Workers of America | 404 U.S. 528 (1972) | Held that a union member could intervene as of right in a suit brought by the Secretary of Labor, establishing a minimal burden for showing inadequate representation. |
| Grutter v. Bollinger | 188 F.3d 394 (6th Cir. 1999) | Allowed minority students to intervene as of right in a challenge to affirmative action policies, finding their interest in diversity was sufficiently distinct from the university's. |
| Natural Resources Defense Council, Inc. v. U.S. Nuclear Regulatory Commission | 578 F.2d 1341 (10th Cir. 1978) | Applied the four-part test for intervention of right, emphasizing the practical impairment standard rather than requiring direct legal impact. |

## Exam Tips

- For intervention of right, the inadequate representation element is the most frequently contested. Courts apply a minimal burden: the applicant need only show that representation may be inadequate.
- Always check timeliness first for both types of intervention. Late intervention can be denied regardless of the strength of the other elements.
- Distinguish intervention from compulsory joinder under Rule 19: the absent party seeks to join via intervention, while an existing party seeks to bring in an absent party via Rule 19.
- In diversity cases, watch for section 1367(b) restrictions on supplemental jurisdiction for intervenors.

## Common Mistakes

- Setting too high a bar for the inadequate representation element; the standard is minimal, requiring only a showing that existing parties may not fully represent the applicant's interests.
- Confusing intervention of right (mandatory if elements are met) with permissive intervention (discretionary), which affects how the court evaluates the application.
- Failing to address subject matter jurisdiction for permissive intervenors, who generally cannot rely on supplemental jurisdiction.

## Mnemonic Or Memory Aid

Rule 24 intervention: Right = TIIA (Timely, Interest, Impairment, Adequacy of representation). Permissive = common question + court discretion.

## Related Rules

- joinder-of-parties-rule-20
- interpleader-rule-22
- class-action-requirements-rule-23
- supplemental-jurisdiction

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Source: [Intervention (Rule 24) — CaseBriefly](https://casebriefly.com/legal-rules/intervention-rule-24)