In a series of recent cases, the ECJ laid the foundations for a new system of international social security protection. European social security legislation in principle designates one Member State as competent, thereby freeing all others from social security responsibilities. For instance, the posting rules entitle workers to carry out work temporarily in a Member State while remaining exclusively subject to the social security legislation of their home State. Disregarding the applicable European and national provisions, the ECJ ruled that, under certain circumstances, a posted worker can also claim benefits under the social security scheme of the host Member State. The ECJ thereby imposes additional social security responsibilities on Member States other than the competent State, allowing a migrant to gain access simultaneously to the social security systems of two or more Member States. Since the origin of EU social security law, the ECJ has used the Treaties to impose obligations on the competent Member States in order to facilitate the free movement of persons.