The case is Dewberry v. Kulongowski, and it involves my favorite court rule, the indispensable party!

From the opinion:

Relators appeal from a judgment dismissing their petition for an alternative writ of mandamus. They argue that the trial court erred in concluding that they failed to establish that they do not have a “plain, speedy and adequate remedy in the ordinary course of the law,” ORS 34.110, and that the trial court misapplied ORCP 29 and ORS 28.110 in the present proceeding. As explained below, we agree with relators in certain respects, albeit at some points for reasons not advanced by the parties, and conclude that relators did not have a “plain, speedy and adequate remedy in the ordinary course of the law,” ORS 34.110, in the form of a declaratory judgment action. Accordingly, we reverse and remand.