The effectiveness of an arbitration clause, as an onerous clause, is subject to specific written approval only when the clause is inserted in contracts with general conditions prepared by only one of the contracting parties, or concluded by signing forms or standard documents. The simple fact that a contractual clause has an onerous nature according to the list in Article 1341 of the Civil Code is not in itself sufficient to require specific written approval.
An arbitration clause contained in professional engagement terms drafted with reference to a specific engagement does not constitute a standard contract intended to regulate an indefinite series of relationships, but a contract drafted for the specific case. Therefore it does not require the double signature referred to in Article 1341 of the Civil Code. Such approval is necessary only when the clause is attached to a contract concluded without negotiation, prepared by one contracting party to regulate an indefinite series of contractual relationships.