Necessary Party

From LegalLanding

A Necessary Party is a person or entity whose interests will be affected by the outcome of a lawsuit, whose absence as a party in the litigation prevents a judgment on all issues, but who cannot be joined in the lawsuit because that would deny jurisdiction to the particular court (i.e. if jurisdiction would shift from a state to federal court). In this uncommon situation, a necessary party who is not in the suit differs from an "indispensable party," who must be joined if the lawsuit is to proceed, and from a "proper party" who may be joined but is not essential.