Necessary party

An indispensable party (also called a required party, necessary party, or necessary and indispensable party) is a party in a lawsuit whose participation is required for jurisdiction or the purpose of rendering a judgment. In reality, a party may be "necessary" but not indispensable. For example, if s/he claims an interest in the litigation, that interest may be impeded if s/he is not joined. That doesn't transform him or her into an indispensable party unless her absence threatens some other party's interest. Often, an indispensable party is any party whose rights are directly affected by disposition of the case. Many jurisdictions have rules which provide for an indispensable party to be joined (brought into the case as a party) at the discretion of the judge. In some cases, the inability to join such a party means that the case must be dismissed. This is outlined in the Federal Rules of Civil Procedure, Rule 19.

The indispensable party is often a prudential standing requirement. That is, while the parties currently involved in litigation have an actual case or controversy, judges will not proceed without the indispensable party. This avoids potential double litigation and possibly inequitable outcomes. In determining whether a party is indispensable, courts generally look to three factors:

In patent law, for example, a patent owner is an indispensable party to a patent infringement suit brought by an exclusive licensee against an alleged infringer. The patent owner's rights would be directly affected by a finding of invalidity or unenforceability of the patent claims. At the same time, if the patent owner is not a party to the case, the alleged infringer could be sued separately by the patent owner, and could end up having to pay two judgments for the same act of infringement.

Once it has been determined that a missing party is indispensable, the court must determine whether it is feasible to join that party to the case. In making this determination, the court will use the same analysis that it uses to determine whether it has jurisdiction over any party. First, it must determine whether it can exercise personal jurisdiction over the party. Second, it must determine whether the exercise of personal jurisdiction will affect its subject matter jurisdiction. In diversity cases, which brought in federal court on the basis of all plaintiffs coming from different states as all defendants, joinder will not be deemed feasible if it destroys diversity.

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