he may not later sue for battery regarding the same occurrence. Joinder of parties Joinder of parties also falls into two categories: permissive joinder and compulsory joinder. Federal Rule of Civil Procedure No. 20 addresses permissive joinder. Permissive joinder allows multiple plaintiffs to join in an action if each of their claims arise from the same transaction or occurrence, and if there is a common question of law or fact relating to all plaintiffs' claims. For example, several landowners may join together in suing a factory for environmental runoff onto their property. Permissive joinder is also appropriate to join multiple defendants, as long as the same considerations as for joining multiple plaintiffs are met. This often occurs in lawsuits regarding faulty products; the plaintiff will sue the manufacturer of the final product and the manufacturers of any constituent parts. The court must have personal jurisdiction over every defendant joined in the action. Compulsory joinder is governed by Federal Rule of Civil Procedure 19, which makes it mandatory that some parties be joined. Parties that must be joined are those necessary and indispensable to the litigation. The rule includes several reasons why this might be true, including if that party has an interest in the dispute that they will be unable to protect if they are not joined. For example, if three parties each lay claim to a piece of property and the first two sue each other, the third will not be able to protect his (alleged) interest in the property if he is not joined. Another circumstance is when a party might end up with inconsistent obligations, for example he may be required by two different courts to grant two different parties exclusive rights to the same piece of property. This is avoided by joining the parties in one lawsuit. However, while "necessary" parties must be joined if that joinder is possible, the litigation will continue without them if joinder is impossible, for example, if the court does not have jurisdiction over the party. By contrast, if "indispensable" parties cannot be joined, the litigation cannot go forward. Courts have some discretion in determining what parties are indispensable, though the Federal Rules provide some guidelines. Timing Rules 18 and 20 have different effects depending on when they are invoked. Joinder may occur as part of an original pleading. There is a discretionary period after the initial filing, during which original