Where an applicant challenges an arbitrator's award on the basis that the arbitrator failed to comply with procedural or statutory requirements (such as failing to assess alternative damages) but does not allege that the arbitrator lacked jurisdiction to hear the matter, the challenge is in substance a review application and not an application for a declaratory order of nullity. Such review applications, being challenges to voidable rather than void acts, fall within the exclusive first-instance jurisdiction of the Labour Court under s 89(di) of the Labour Act, not the High Court. The mere fact that an arbitrator's decision is incomplete does not render it void ab initio; it may be voidable and subject to review in the Labour Court.