Article 387 Federal Labor Law

The employer that employs employees who are members of a labor union shall have the obligation to enter into a collective contract with it, when it so requests; in order to comply with the principles of representativeness in the union organizations and of certainty in the signing, registration and deposit of the collective employment contracts, the requesting labor union must previously have the Certificate of Representativeness issued by the Federal Center for Conciliation and Labor Registration, referred to in Article 390 Bis.

If the employer refuses to sign the contract, the employees may exercise the right to strike consigned in Article 450; the Certificate of Representativeness proves that the labor union has the representation of the employees, for which reason it must be accompanied with the strike notice as a requirement under the terms of Article 920 of this Law.

The Certificate of Representativeness referred to in Article 390 Bis shall have a validity of six months from the date on which it is issued. In the event that the notifying labor union carries out the strike in the workplace, the validity of said certificate shall be extended until said conflict concludes, for which reason during its validity, no other request shall be processed, nor shall another or other labor unions be admitted as part of the procedure.