Iowa Code § 602.10115: Proof of authority.

The court may, on motion of either party and on the showing of reasonable grounds therefor, require the attorney for the adverse party, or for any one of the several adverse parties, to produce or prove by the attorney’s own oath, or otherwise, the authority under which the attorney appears, and, until the attorney does so, may stay all proceedings by the attorney on behalf of the parties for whom the attorney assumes to appear.