Contract for the purchase and sale of shares at a variable price with an arbitration clause. Filing of an enforcement action by the creditor. Institution of arbitration proceedings by the debtor in which the arbitral tribunal has already recognized its jurisdiction. Kompetenz-kompetenz principle. Inadmissibility of the debtor's petition to challenge execution proceedings. Matter subject to the arbitration proceedings. After the levy in aid of execution, "the enforcement court must stay its course, as it would if a debtor's petition to challenge execution proceedings had been filed." Emergency relief granting stay of execution to the special appeal suspending the judicial enforcement action: