When an opposition is referred to it, the National Institute of Industrial Property shall observe and observe itself the principle of contradiction. It may not base its decision on pleas, explanations or documents put forward or produced by the parties without the latter having been given the opportunity to debate them in adversarial proceedings. The parties to the opposition are required to expressly state their claims and the factual and legal arguments on which each of their claims is based. All communications addressed to the Institute shall be made, on pain of inadmissibility, in accordance with the terms and conditions laid down by decision of the Director General of the National Institute of Industrial Property.