A necessary party in a lawsuit is a person or entity whose connection to the dispute is strong enough that the case cannot fairly move forward without them. Federal Rule of Civil Procedure 19 calls these people “required parties” and tells courts they must be added when possible. When they can’t be added, the court may have to dismiss the case entirely.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
Who Counts as a Required Party
Rule 19(a) sets out two situations where someone qualifies. The first is simpler: the court cannot give the people already in the case complete relief without that person present. If the judge’s order would leave part of the dispute unresolved because someone important is missing from the room, that someone has to be brought in.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
The second applies when a person claims an interest in whatever the lawsuit is about, and going ahead without them would either harm their ability to protect that interest or put an existing party at risk of conflicting obligations. The second half of that test matters in practice. Picture a defendant who could be ordered to hand over the same property or pay the same debt to two different claimants in two different proceedings, with no way to satisfy both rulings. Rule 19 is designed to prevent that trap.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
A Note on “Indispensable Party”
Older cases and legal materials often use the phrase “indispensable party” for someone whose absence requires dismissal. The 2007 amendments to Rule 19 dropped that label as redundant. Today the rule just talks about “required parties” under 19(a), and whether the case has to be dismissed when such a person can’t be added is a separate question answered under 19(b).1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
Required Parties Are Different From Permissive Parties
Rule 19 deals with people who must be in the lawsuit. Rule 20 deals with people who may be in it. Under Rule 20, individuals can voluntarily join as co-plaintiffs if they share a right to relief arising from the same transaction and their claims share at least one common question of law or fact. Defendants can be grouped together under the same conditions.2Legal Information Institute. Federal Rules of Civil Procedure Rule 20
The difference is consequence. Leaving out a permissive party just makes for a narrower lawsuit. Leaving out a required party can end the case. When the issue is raised, the first thing to figure out is which rule applies.
How a Required Party Gets Added
Once someone qualifies under Rule 19(a), the court does not have discretion to let it slide. The rule says that if a required person has not been joined, the court “must order that the person be made a party.” Two practical conditions apply. The person has to be reachable through service of process, and adding them cannot destroy the court’s subject-matter jurisdiction. In federal court, that most often means the new party cannot wipe out the diversity of citizenship that gave the court authority over the case to begin with.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
Most added parties come in as defendants. If someone logically belongs on the plaintiff’s side but refuses to participate, the court can designate them an “involuntary plaintiff,” a procedural device that keeps the case properly structured even when the person would rather stay out of it.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
Rule 21 gives courts broad authority to add or drop parties at any stage of the litigation, either on a party’s motion or on the court’s own initiative. That flexibility matters when joinder issues surface late.3Legal Information Institute. Federal Rules of Civil Procedure Rule 21
How the Issue Gets Raised
Either side can bring a missing-party problem to the court’s attention by filing a motion under Rule 12(b)(7) for failure to join a required party. The court can also raise the issue on its own at any point. Joinder differs here from defenses like personal jurisdiction or improper venue, which are waived if not raised early. Under Rule 12(h)(2), a Rule 19 objection can be raised in a later pleading, through a motion for judgment on the pleadings, or even at trial.4Legal Information Institute. Federal Rules of Civil Procedure Rule 12
The staying power of this defense reflects how seriously courts take it. A missing required party is not a technicality that fades with time; it goes to whether the court can deliver a fair, complete judgment at all.
Common Situations That Trigger Required Joinder
Certain disputes generate joinder issues more reliably than others. Spotting the pattern early can prevent a dismissal that a properly named complaint would have avoided.
Real Property Disputes
When more than one person holds a legal interest in the same piece of real estate, litigation over that property usually requires every owner at the table. A co-owner suing to partition the land or force a sale cannot get a meaningful order if the other owners are absent, because the court cannot divide property or transfer title when someone with a stake has had no chance to defend their share. The same logic reaches boundary disputes, easement claims, and foreclosures involving multiple lien holders.
Contracts With Multiple Parties
When a lawsuit challenges the validity of an entire contract, every signer generally needs to be in the case. Partnership dissolution is the textbook example. If one partner sues to wind down the business, every partner has a direct stake in how assets are distributed and debts allocated. Proceeding without all of them risks a judgment that is unenforceable or unfair to those who were never heard.
Trust and Estate Litigation
Challenges to a trust’s distribution typically require all named beneficiaries to participate. Without them, the court cannot finalize a plan that binds everyone, which almost guarantees follow-up litigation from any beneficiary left out. The same problem shows up in estate disputes when multiple heirs contest a will or an executor’s decisions.
What Happens When a Required Party Can’t Be Joined
Sometimes a required party simply cannot be brought into the case. They may live outside the court’s jurisdictional reach. Adding them might destroy diversity jurisdiction. Or they may enjoy sovereign immunity that prevents them from being sued at all. When joinder is not feasible, the court does not automatically dismiss. Rule 19(b) requires the judge to weigh four factors before deciding whether the lawsuit can fairly continue or must be thrown out.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
Courts look at:
- How much harm a judgment might cause to the absent person, or to the parties already in the case, if the court goes ahead.
- Whether the court can shape the relief, add protective provisions, or take other measures to reduce that harm.
- Whether a ruling issued without the missing party would actually resolve the dispute or would be incomplete.
- Whether the plaintiff has another forum available if the case is dismissed.
No single factor controls. Courts are supposed to take a practical, case-by-case approach rather than apply a rigid formula.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
A dismissal under Rule 19(b) is generally without prejudice. The plaintiff can usually refile in a courtroom that can reach everyone, often state court or a different federal district. The case is not dead; it just needs a bigger room.1Legal Information Institute. Federal Rules of Civil Procedure Rule 19
Sovereign Immunity as a Joinder Barrier
Some of the hardest joinder problems involve government entities and tribal nations that cannot be sued without their consent. When a required party holds sovereign immunity, joinder is impossible no matter what else is true. The Supreme Court addressed this directly in Republic of the Philippines v. Pimentel, holding that when a sovereign entity is a required party and asserts immunity, dismissal under Rule 19(b) is the likely outcome, even if it leaves the plaintiff with no alternative forum.5Justia. Republic of Philippines v. Pimentel, 553 US 851 (2008)
The Court reasoned that sovereign immunity would mean little if a federal court could proceed to make consequential rulings affecting the sovereign’s interests while the sovereign sat outside the case objecting. Where sovereign immunity and the claims of the absent party are not frivolous, dismissal “must be ordered where there is a potential for injury to the interests of the absent sovereign.”5Justia. Republic of Philippines v. Pimentel, 553 US 851 (2008)
Tribal sovereign immunity creates the same dynamic. A tribe can only be sued when Congress has authorized the suit or the tribe has waived its own immunity. When a tribe is a required party and asserts immunity, courts have frequently dismissed under Rule 19(b), even when dismissal effectively ends the plaintiff’s ability to obtain any relief. Lower courts have sometimes distinguished Pimentel, for instance by concluding that an existing party adequately represents the sovereign’s interests or that the absent sovereign’s stake is financial rather than legal, but these are exceptions to a general pattern that favors dismissal.