FEDERAL RULES OF CIVIL PROCEDURE

IV. Parties

Rule 24— Intervention

(a) Intervention of Right. Upon timely application anyone shall be permitted to intervene in an action:

(1) when a statute of the United States confers an unconditional right to intervene; or

relating to the property or transaction which is the subject of the action and the (2) when the applicant claims an interest applicant is so situated that the disposition of the action may as a practical matter impair or impede the applicant's ability to protect that interest, unless the applicant's interest is adequately represented by existing parties.

(b) Permissive Intervention. Upon timely application anyone may be permitted to intervene in an action:

(1) when a statute of the United States confers a conditional right to intervene; or

(2) when an applicant's claim or defense and the main action have a question of law or fact in common. When a party to an action relies for ground of claim or defense upon any statute or executive order administered by a federal or state governmental officer or agency or upon any regulation, order, requirement or agreement issued or made pursuant to the statute or executive order, the officer or agency upon timely application may be permitted to intervene in the action. In exercising its discretion the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.

(c) Procedure. A person desiring to intervene shall serve a motion to intervene upon the parties as provided in Rule 5. The motion shall state the grounds therefor and shall be accompanied by a pleading setting forth the claim or defense for which intervention is sought. The same procedure shall be followed when a statute of the United States gives a right to intervene. When the constitutionality of an act of Congress affecting the public interest is drawn in question in any action in which the United States or an officer, agency, or employee thereof is not a party, the court shall notify the Attorney General of the United States as provided in Title 28, U.S.C. § 2403. When the constitutionality of any statute of a State affecting the public interest is drawn in question in any action in which that State or any agency, officer, or employee thereof is not a party, the court shall notify the attorney general of the State as provided in Title 28, U.S.C. § 2403. A party challenging the constitutionality of legislation should call the attention of the court to its consequential duty, but failure to do so is not a waiver of any constitutional right otherwise timely asserted.

[As amended Dec. 27, 1946, eff. Mar. 19, 1948; Dec. 29, 1948, eff. Oct. 20, 1949; Jan. 21, 1963, eff. July 1, 1963; Feb. 28, 1966, eff. July 1, 1966; Mar. 2, 1987, eff. Aug. 1, 1987; Apr. 30, 1991, eff. Dec. 1, 1991.]