What is one key aspect of compulsory joinder?

Compulsory joinder refers to the requirement that certain parties must be joined in a lawsuit to ensure that the court can resolve all related issues in a single proceeding. This is aimed at avoiding multiple lawsuits and ensuring that all parties with a significant interest in the outcome are present. The essence of compulsory joinder is rooted in the idea of complete justice; it prevents situations where a judgment may be rendered without all necessary parties involved, potentially leading to inconsistent verdicts or unfair outcomes.

Choosing the option regarding the mandate for joining all interested parties reflects this principle directly. In cases where an absent party has an interest in the subject matter, their presence is crucial for the court to make a fully informed decision, thereby underlining why their inclusion is necessary from a legal standpoint.

Other options may suggest different misunderstandings about how compulsory joinder functions, focusing on aspects such as the filing of independent claims or simultaneous filings, which do not capture the core requirement that all interested parties must be included to ensure the efficacy and fairness of the judicial process.