The Federal Rules of Civil Procedure
Plaintiff and Defendant; Capacity; Public Officers
(a) Real Party in Interest.
(1) Designation in General. An action must be prosecuted in the name of the real party in interest. The following may sue in their own names without joining the person for whose benefit the action is brought:
(A) an executor;
(B) an administrator;
(C) a guardian;
(D) a bailee;
(E) a trustee of an express trust;
(F) a party with whom or in whose name a contract has been made for another's benefit; and
(G) a party authorized by statute.
(2) Action in the Name of the United States for Another's Use or Benefit. When a federal statute so provides, an action for another's use or benefit must be brought in the name of the United States.
(3) Joinder of the Real Party in Interest. The court may not dismiss an action for failure to prosecute in the name of the real party in interest until, after an objection, a reasonable time has been allowed for the real party in interest to ratify, join, or be substituted into the action. After ratification, joinder, or substitution, the action proceeds as if it had been originally commenced by the real party in interest.
(b) Capacity to Sue or Be Sued. Capacity to sue or be sued is determined as follows:
(1) for an individual who is not acting in a representative capacity, by the law of the individual's domicile;
(2) for a corporation, by the law under which it was organized; and
(3) for all other parties, by the law of the state where the court is located, except that:
(A) a partnership or other unincorporated association with no such capacity under that state's law may sue or be sued in its common name to enforce a substantive right existing under the United States Constitution or laws; and
(B) 28 U.S.C. §§754 and 959(a) govern the capacity of a receiver appointed by a United States court to sue or be sued in a United States court.
(c) Minor or Incompetent Person.
(1) With a Representative. The following representatives may sue or defend on behalf of a minor or an incompetent person:
(A) a general guardian;
(B) a committee;
(C) a conservator; or
(D) a like fiduciary.
(2) Without a Representative. A minor or an incompetent person who does not have a duly appointed representative may sue by a next friend or by a guardian ad litem. The court must appoint a guardian ad litem—or issue another appropriate order—to protect a minor or incompetent person who is unrepresented in an action.
(d) Public Officer's Title and Name. A public officer who sues or is sued in an official capacity may be designated by official title rather than by name, but the court may order that the officer's name be added.