Analyzing civil procedure rules in the case of multiple parties

In the case of multiple potential parties of litigation, some delicate issues can be raised that is able to prevent judge from trying substance of the claim. If there is solidarity among plaintiffs, every plaintiff can litigate. In the absence of solidarity, severability or non-severability of relief has a determining role in permitting individual litigation and is the test for adjudicating the substance of the action by judge. In Iran’s law various plaintiffs with common or similar issues of law or fact, are not allowed to sue against common defendant in one statement of claim, but in American law such a device with the title of compulsory or permissive joinder has been devised. The absence of joinder in Iran’s law is followed by inefficiency, wasting resources and sometimes conflicting judgments that undermines judiciary’s reputation. In the case of various defendants and their solidary obligation, the plaintiff can start an action against all or some of them, but when there is no solidarity among them, severability of relief is the test for litigating against some of them. Whenever there are many potential plaintiffs and defendants, depending upon solidarity among plaintiffs and defendants and relief severability, miscellaneous assumptions can be drawn that are governed by different legal injunctions.