In this article, a class action under the federal rules of civil procedure and a class action under the state rules of civil procedure were compared. It is not virtually easy to compare all states, and I focused on the state of Missouri that adopted the federal rule on average, and the state of Mississippi that did not adopt a class action.
 Most states in the United States used the Federal Rules of Civil Procedure, with minor modifications, without major changes. In the case of Missouri, it was found that the federal rules were in fact used as they were and some of the requirements of the representative party were interpreted with some flexibility. On the other hand, Mississippi, when it enacted the state civil procedure rules in 1982, refused to accept class action system and operated its case law and statutory laws independently. As a result, many precedents regarding class action in Mississippi have been upheld : a class action without explicit statutes and provisions is impossible, a class action that existed before the 1980s in lower courts is not possible, and unlimited permissive joinder and consolidation that were substitutes for class action are rejected.
 Still, there were lessons to be learned from the case of Mississippi. First, in spite of no class action in Mississippi, most relief can be obtained through federal procedure. However, in the case of Mississippi's own human rights violations or small businesses in Mississippi, it is necessary to introduce a class action in the state.
 Second, the class action in Mississippi is very closely related to tort law reform. In particular, it is worth noting that proportional liability and limitation of liability introduced in the state of Mississippi should be considered as an alternative in order to expand the class action system in Korea. This means that it is necessary to balance what kind of discussions were made for the defense of the defendant while discussing class action and punitive damages for the relief of the plaintiff. At least in the case of companies with minor negligence, as a feasible method, it seems that the defendant should be sufficiently defended by assuming the case of faithfully fulfilling the duty of care.
 Third, the attempt to operate Rule 20(permissive joinder of parties) and Rule 42 (consolidation) of the Mississippi State Rules as a substitute of class action can be highly evaluated. This is because the attempt to quickly relieve small damages of large number of people in one procedure can be evaluated as an attempt to guarantee the citizens' right to access justice. However, this has fundamental limitations in relation to class action. In Rule 20 of the State Rule, it seems that it is difficult to define a class action only by the commonality of factual issues or legal issues, and the problem of conflict of interest is also difficult to resolve.
 In Korea, there is also a discussion on the addition of an ordinary co-litigation, but this is a problem that should be applied to an ordinary co-litigation, and it is not intended to be converted into a class action. However, although permissive joinder as the addition of an ordinary co-litigation is a legal doctrine that has been abandoned by the Mississippi state precedent, I think that the attempt to resolve collective disputes through permissive joinder is positive enough.
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