The internal regulations must in principle respect any provision which is of a higher rank. Thus, any change in the internal regulations must comply with the provisions of laws, regulations and agreements. Similarly, a change to the internal regulations may not derogate from the employment contract, except in a manner which is more favourable to the employees.
If they have been formally accepted by the employee within the employment contract, the internal regulations will be regarded as an integral part of the employment contract. The internal regulations will then become a contractual provision and no change thereto may be made except with the agreement of the employee or pursuant to the procedure for substantial amendment of the employment contract to the detriment of the employee.
Thus, any change unfavourable to the employee affecting an essential clause of the employment contract will, on pain of nullity, have to be notified to the employee in the manner and within the time-limits laid down for dismissal with notice, and indicate the date on which it takes effect. In such case, the employee may ask the employer to give the reasons for the change and the employer is required to set out those reasons in the manner and within the time limit provided for statements of reasons for dismissal with notice.
In general, the employer must make certain that the employee has been able to familiarise himself with the existing internal regulations when the contract is entered into and, if appropriate, provide him with a copy.
In the event of a change to the internal regulations, in compliance with the principles set out above, the employer is required to give notice thereof to the employee.
It should be noted that all clauses of the employment contract or of the internal regulations under which the employees agree to any unilateral modification of the content of the employment contract or of the internal regulations by the employer are void and wholly ineffective.