Generally, an order allowing or denying the substitution of parties is not directly appealable. Courts have repeatedly held that for a judgment to be final, it must determine the controversies between the parties over the subject matter of the litigation. An order is appealable as a final order under 28 U.S.C. § 1291 if the order: (1) conclusively determines the disputed question; (2) resolves an important issue completely separate from the merits of the action; and (3) is effectively unreviewable on appeal from a final judgment.[i] For instance, a dispute is not finally determined by an order removing someone as next friend and appointing another as next friend for the real party plaintiff. [ii]
Unless a statute specifically permits the review of an order of the court, suits which are interlocutory in nature and has nothing to do with the merits of the case are not appealable.
However, orders of substitution may be appealable under special statutory provisions allowing appeals from interlocutory orders affecting substantive rights and liabilities of the parties.
On the other hand, there are cases which states that courts have inherent discretionary power to proceed independent of statute. [iii] Such discretionary power allows a trial court to substitute a member of a class for whose benefit the action was brought as representative plaintiff following the death or disqualification of the original plaintiff. [iv]
Parties have no absolute right to intervene in cases, and the right to intervene in a suit may be denied by the court in the exercise of its discretion, “and the discretion will usually be so exercised when there is no suggestion of fraud or collusion or that the representative will not act in good faith for the protection of all interests represented by him.”[v]
[i] Gulfstream Aerospace Corp. v. Mayacamas Corp., 485 U.S. 271 (U.S. 1988)
[ii] Henderson v. Shell Oil Co., 143 Tex. 142 (Tex. 1944)
[iii] Johnson v. Hartford Acci. & Indem. Co., 187 Minn. 186 (Minn. 1932)
[iv] Siegel v. Archer, 212 Ind. 599 (Ind. 1937)
[v] Barnard v. Kruzan, 221 Ind. 208 (Ind. 1943)