Even if the contract provides for the free appointment of the arbitrator by both contracting parties, the appointment must comply with the rules on disqualification and recusal of adjudicators set forth in procedural legislation. Arbitrator who signed the contract as a witness, acts as a lawyer for the business group of a party, and has already expressed his views on the dispute. Admissibility of the action under Article 7 for the replacement of the challenged arbitrator: