Commentaries: Art. 356a

Any clause in a collective employment contract or individual agreement between the contracting parties intended to compel an employer or employee to join a contracting association is void.
Any clause in a collective employment contract or individual agreement between the contracting parties intended to exclude or restrict the practice of a particular profession or occupation by an employee or his acquisition of the necessary vocational training is void.
The clauses and agreements referred to in the previous paragraph are valid by way of exception if they are justified by overriding interests that warrant protection, in particular personal health and safety or the quality of work; however, denial of access to the profession is not an interest that warrants protection.