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Rule 24.Intervention

Effective July 1, 1974 · Last verified June 26, 2026

In one sentenceRule 24 lets a non-party join an existing case—as of right when its interest could be impaired, or by the court's permission when it shares a common question—and requires notice to the Attorney General when a statute's constitutionality is challenged.

Full Text of Rule 24

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

(a) Intervention of Right. Upon timely application anyone shall be permitted to intervene in an action: (1) when a statute of the Commonwealth confers 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 action and he is so situated that the disposition of the action may as a practical matter impair or impede his 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 Commonwealth 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.
(d) Intervention by the Attorney General. When the constitutionality of an act of the legislature or the constitutionality or validity of an ordinance of any city or the by-law of any town is drawn in question in any action to which the Commonwealth or an officer, agency, or employee thereof is not a party, the party asserting the unconstitutionality of the act or the unconstitutionality or invalidity of the ordinance or by-law shall notify the attorney general within sufficient time to afford him an opportunity to intervene.
End

Rule History

Effective July 1, 1974.

Reporter’s Notes

(1973)

Rule 24(a), with the exception of the substitution of "Commonwealth" for the "United States" is identical to Federal Rule 24(a). It permits the intervention of a party as a matter of tight in two instances: (1) where permitted by statute and (2) where the disposition of the action may as a practical matter impair or impede the applicant's ability to protect his claimed interest, unless such interest is adequately represented by existing parties.

Prior to a 1966 amendment to Federal Rule 24, apart from statutory authorization, intervention was allowed as a matter of right only upon a showing (1) that the applicant might be bound by a judgment in the action, and that existing parties would inadequately represent his interests; or (2) that the applicant would be adversely affected by a distribution or other disposition of property in the custody or subject to the control or disposition of the court.

The Advisory Committee on the Federal Rules felt that the "res judicata" or "fund" requirements of the former Federal Rule 24(a) were unnecessarily restrictive. If the interests of an absentee who would be substantially affected in A practical sense by the determination are not adequately represented by existing parties, he should, as a matter of right, be allowed to intervene.

Its amended version of Federal Rule 24(a) coordinates more closely intervention with joinder (Rule 19) and class actions (Rule 23). The amendment provides that an applicant is entitled to intervene in an action when his position is comparable to that of a person under Rule 19(a)(2)(1) unless his interest is already adequately represented by existing parties.

Adequacy of representation under Rule 24(a) is not confined to formal representation like that provided by a trustee for his beneficiary or a representative party in a class action for a member of the class. Ford Motor Co. v. Bisanz Bros. Inc., 249 F.2d 22 (8th Cir.1957) presents a good illustration of practical representation and of the wisdom of eliminating the res judicata requirement of the former version of Federal Rule 24(a). Ford involved an action by property owners against a railroad company to enjoin the operation of freight cars on certain trackage. Ford, which owned an assembly plant which was serviced by this particular trackage, sought to intervene under Federal Rule 24(a). The United States Court of Appeals vacated an order of the District Court and allowed Ford to intervene. On the argument of plaintiff that Ford should not be allowed to intervene because it would not be bound by any judgment against the railroad, the Court held that a judgment against the railroad would have the practical effect of denying Ford a service essential to its operation. As amended, Rule 24(a) codifies this reasoning.

Apart from a few isolated situations covered by statute (see G.L. c. 12, § 8; G.L. c. 149, § 29; G.L. c. 151D, § 3; G.L. c. 241, § 6), intervention as a matter of right did not exist under prior Massachusetts practice.

A person could intervene in Massachusetts only upon a showing that he had a substantial interest in the subject matter of the litigation (Check v. Kaplan, 280 Mass. 170, 178, 182 N.E. 305, 308 (1932)). In all cases a motion to intervene was addressed to the sound judicial discretion of the presiding judge; his decision would not be reversed unless it clearly appeared that there has been an abuse of such discretion. Haverhill v. Di Burro, 337 Mass. 230, 235, 236, 148 N.E.2d 642, 645, 646 (1958).

Rule 24(b) provides for permissive intervention when allowed by statute or where an applicant's claim or defense and the main action have a question of law or fact in common. The purpose of Rule 24(b) is to facilitate the disposal in one action of claims involving common questions of law or fact, thus avoiding both court congestion and undue delay and expense to all parties. On the other hand, one could argue that intervention may unduly delay or prejudice the adjudication of the right of the original parties.

Rule 24(b) clearly alters Massachusetts practice which required as a condition for the allowance of intervention a showing by the applicant of a substantial interest in the subject matter of the litigation. See Check v. Kaplan, supra.

Rule 24(c) regulates the form of the prospective intervenor's notice to the parties.

Under Rule 24(d), the obligation to notify the attorney general that the constitutionality of an act of the legislature or of a municipality is being questioned in the action is placed upon the party asserting the unconstitutionality of the act (or the unconstitutionality or invalidity of an ordinance or by-law) rather than, as in Federal Rule 24(c), on the court.

Plain-English Summary

Rule 24 brings outsiders into a case. A person may intervene as of right when a statute gives an unconditional right, or when the person claims an interest in the property or transaction at stake that the case could, as a practical matter, impair—unless existing parties already protect that interest.

The court may also permit intervention, in its discretion, when a statute confers a conditional right or when the would-be intervenor's claim or defense shares a common question of law or fact with the main action; the court weighs whether intervention would unduly delay or prejudice the original parties. Either way, the person files a motion stating the grounds, accompanied by a pleading setting out the claim or defense.

Rule 24(d) adds a specific notice requirement: when a case questions the constitutionality of a statute, or the validity of a city ordinance or town by-law, and the Commonwealth is not already a party, the challenger must notify the Attorney General in time to intervene.

Frequently Asked Questions

What is the difference between intervention of right and permissive intervention?

Intervention of right must be allowed when a statute grants an unconditional right or when the applicant has an interest the case could practically impair and no existing party adequately protects it. Permissive intervention is discretionary—allowed when there is a conditional statutory right or a common question of law or fact, weighing delay and prejudice.

How does a person intervene?

By serving a motion to intervene under Rule 5 that states the grounds, accompanied by a pleading setting forth the claim or defense for which intervention is sought.

When must the Attorney General be notified?

When a case draws into question the constitutionality of a statute, or the validity of a municipal ordinance or by-law, and the Commonwealth is not a party. The challenger must notify the Attorney General in time to intervene.

Source & verification. Rule text, Rule History, and Reporter’s Notes reproduced verbatim from the Massachusetts Rules of Civil Procedure as published by the Massachusetts Trial Court Law Libraries. Promulgated by the Supreme Judicial Court of Massachusetts. Last verified June 26, 2026. · Official text
Also known as: interventionintervenemotion to interveneintervention of right