Title IV: Parties · Last amended July 1, 2016 · Last verified July 14, 2026
In one sentenceRule 24 lets a person with a real stake in a pending lawsuit join the case, either as of right when a statute or an unprotected interest demands it, or with the court's permission when their claim or defense shares a common question with the case already filed.
(a)Intervention of right. On timely motion, the court must permit anyone to intervene who:
(1)is given an unconditional right to intervene by an Idaho 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.
(1)In general. On timely motion, the court may permit anyone to intervene who:
(A)is given a conditional right to intervene by an Idaho 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.
Amendment History
(Adopted March 1, 2016, effective July 1, 2016.)
Plain-English Summary
A lawsuit sometimes touches people who were never named as parties, and Rule 24 gives them a door into the case. Intervention as of right applies in two situations: when an Idaho statute grants an unconditional right to join, or when the person claims an interest in the property or transaction at stake and no one already in the case will adequately protect that interest. If the motion is timely and either condition is met, the court must let the person in; it has no discretion to keep them out.
Permissive intervention works differently. The court may allow someone to join, rather than having to, when a statute grants a conditional right or when the person's claim or defense shares a common question of law or fact with the pending case. Government agencies get a similar path when a party's claim or defense rests on a statute, executive order, or regulation the agency administers. In deciding whether to allow permissive intervention, the court has to weigh whether adding the newcomer will unduly delay or prejudice the original parties. Anyone seeking to intervene, whether as of right or by permission, must serve a motion on the existing parties and attach a proposed pleading laying out the claim or defense they want to bring.
Frequently Asked Questions
What is the difference between intervention of right and permissive intervention?
Intervention of right means the court must let the person join once the timing and interest requirements are met. Permissive intervention means the court has discretion to allow it, typically because the newcomer's claim or defense shares a common question with the pending case.
What has to be filed to intervene in a case?
A motion that states the grounds for intervention, served on the existing parties, along with a pleading setting out the claim or defense the intervenor wants to assert.
Can a government agency intervene in a private lawsuit?
Yes. If a party's claim or defense is based on a statute, executive order, or related regulation that a federal or state agency administers, the agency may seek permissive intervention.
What does the court consider before allowing permissive intervention?
Whether letting the person join will unduly delay the case or prejudice the rights of the parties already in it.
Does it matter how late in the case someone tries to intervene?
Yes. Both forms of intervention require a timely motion, and a court can deny intervention if the request comes too late in the proceedings.
Source & verification. Rule text
are reproduced verbatim from the Idaho Rules of Civil Procedure, adopted by the
Supreme Court of Idaho. Last verified July 14, 2026. ·
Official source
Also known as:intervene in a lawsuit idahointervention of rightpermissive intervention rulejoin a pending casethird party wants to join lawsuit