Indispensable party

An indispensable party is someone whose interests are so wrapped up in the lawsuit that proceeding without them would be unjust to them or to the existing parties. If joining the missing party is not possible, for instance because joining them would destroy jurisdiction, the court has to decide whether the case can go forward at all. The analysis weighs prejudice to the absent person, the adequacy of any judgment, and whether the plaintiff has another adequate forum. If the missing party is truly indispensable, the case is dismissed. The concept lives in Federal Rule of Civil Procedure 19 and similar state rules.