Motion to Intervene Normally, a lawsuit involves the plaintiffs (who bring the suit), and the defendants (whom the suit is brought against).  Sometimes, a person who is not a party to a lawsuit in progress wants to become a party.  Such a party must file a Motion to Intervene.  Generally, to be admitted into the lawsuit, the intervenor must have an interest in the subject matter of the original suit. A motion to intervene in a case in Federal Court is addressed by Rule 24 of the Federal Rules of Civil Procedure.  It provides in part that: (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 (2) when the application claims an interest relating to the property or transaction which is the subject of the action and the 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.