2. It shall not be lawful to derogate in private contracts of employment from the principle of equality of treatment referred to in paragraph 1 of the present article. 3. States Parties shall take all appropriate measures to ensure that migrant workers are not deprived of any rights derived from this principle by reason of any irregularity in their stay or employment. In particular, employers shall not be relieved of any legal or contractual obligations, nor shall their obligations be limited in any manner by reason of any such irregularity. Article 26 1. States Parties recognize the right of migrant workers and members of their families: (a) To take part in meetings and activities of trade unions and of any other associations established in accordance with law, with a view to protecting their economic, social, cultural and other interests, subject only to the rules of the organization concerned; (b) To join freely any trade union and any such association as aforesaid, subject only to the rules of the organization concerned; (c) To seek the aid and assistance of any trade union and of any such association as aforesaid. 2. No restrictions may be placed on the exercise of these rights other than those that are prescribed by law and which are necessary in a democratic society in the interests of national security, public order (ordre public) or the protection of the rights and freedoms of others. Article 27 1. With respect to social security, migrant workers and members of their families shall enjoy in the State of employment the same treatment granted to nationals in so far as they fulfil the requirements provided for by the applicable legislation of that State and the applicable bilateral and multilateral treaties. The competent authorities of the State of origin and the State of employment can at any time establish the necessary arrangements to determine the modalities of application of this norm. 119