Article 395 Federal Labor Law

In the collective employment contract, it may be established that the employer will admit exclusively as employees those who are members of the contracting labor union. This clause and any others that establish privileges in its favor may not be applied to the detriment of the employees who are not part of the labor union and who already render their services in the company or establishment prior to the date on which the labor union requests the execution or revision of the collective employment contract and the inclusion in it of the exclusion clause. The union sanction imposed on the employee may not affect his permanence in employment or his working conditions.