The courts are entrusted with the implementation of required joinder of parties under Federal Rule of Civil Procedure 19. Indeed, the courts have substantial discretion to determine, under the considerations listed in Rule 19(b), whether to continue the litigation without the person who should be joined in pending litigation or to dismiss the action because such a person cannot be joined. Therefore, the courts are asked to weigh the factors under Rule 19(b) and recognize that one factor can be more important than others in a given case or other factors not listed in Rule 19(b) can be important in a particular case. The exercise of this discretionary power is crucial in understanding when the required joinder of parties is actually feasible. There is a range of possibilities for how narrowly or broadly judges might exercise this power. Whether an individual judge exercises this power broadly or narrowly in a particular dispute, she always needs to wait for cases to come to her. Nevertheless, this question has deep roots in American legal tradition. The concept of judicial discretion under Rule 19(b) has gradually focused not only on the protection of the interests of absent persons as well as those already before the courts from the risk of legal or practical damage but also on the protection of public interests in an adequate—meaning, efficient, coherent, and final—judgment.

The comparative analysis of Rule 19(b) and legal rules governing the required joinder of parties in Italian and German legal systems suggests some thoughts about a better way to define the judicial discretion in determining whether a person who should be joined is actually indispensable—that is, essential to dismiss the action when that person cannot be joined. According to Italian and German legal traditions, persons can be qualified as indispensable to the purpose of required joinder of parties when their interest to be joined in pending litigation is strictly embedded in the factual specificities of the case. Since the civil law tradition is rights-focused, these specificities are mainly described in terms of co-ownership of individual rights, so that the adjudication must be coherently rendered in favor of all the co-owners of a given right. Such an approach seems to be a useful means of fortifying the American doctrine of judicial discretion under Rule 19(b).