Between the multi-company agreement and the company collective bargaining agreement, there is no relation between the parent and executive act, and the parties to the agreement are not superior to the parties to the enterprise agreement.
The only restriction on the freedom of parties to an establishment agreement results from the principle of advantage, according to which the provisions of the establishment agreement may not be less favorable to employees than the provisions of the multi-establishment agreement covering them (Article 24126 § 1 of the Labor Code).
Therefore, the provisions of the multi-company agreement, obliging the parties to the establishment agreement to:

• introducing specific regulations,
• regulating a given issue in a specific manner or prohibiting its regulation, as well as otherwise interfering with the right of the parties to the establishment agreement to autonomously shape the content of the establishment agreement, violate the provision of Art. 240 § 3 of the Labor Code, i.e. the rights of third parties, and therefore are unlawful.

Source: http://www.dialog.gov.pl/dialog-krajowy/uklady-zbiorowe-pracy/warto-wiedziec-o—czyli-regulacje-szczegolne/