Intervention (law) - United States Practice

United States Practice

In the United States federal courts, intervention is governed by Rule 24 of the Federal Rules of Civil Procedure.

Part (a) of Rule 24 governs intervention of right. A potential party (called the applicant) has the right to intervene in a case either (1) when a federal statute explicitly confers upon the applicant an unconditional right to intervene or (2) when the applicant claims an interest relating to the property or transaction which is the subject of the lawsuit. In the second situation, in order to be admitted as an intervenor, the applicant must show that its ability to protect its interest would be impeded by disposition of the case and that its interest is not adequately represented by the current parties to the case.

Part (b) of Rule 24 governs what is called permissive intervention, which is subject to the discretion of the judge hearing the case. An applicant may be permitted by the court to intervene (1) when a federal statute confers upon the applicant a conditional right to intervene or (2) when the applicant's claim or defense shares a common question of law or fact with the main action. Agents of the federal or state government may be permitted by the court to intervene when a party to a case relies on a federal or state statute or executive order, or any regulation promulgated thereunder, for its claim or defense.

In both intervention of right and permissive intervention, the applicant must make a timely application to be heard. The applicant cannot sit on its rights; it must intervene as soon as it has reason to know that its interest may be adversely affected by the outcome of the pending litigation. The applicant must serve its motion to intervene on the parties to the case and explain its reasons for intervening in the motion papers. In addition, U.S. federal law does not allow the procedure of intervention to violate the requirements of diversity jurisdiction. The court must have either diversity jurisdiction or federal question jurisdiction over the intervenor's claim. While supplemental jurisdiction is not permitted for intervention claims under 28 U.S.C. § 1367(b) when the original claim's federal jurisdiction was based solely on diversity, supplemental jurisdiction is permitted when the claims are so related that they form the same case or controversy.