As far as I am aware, it was always thus.  CF Thus Irish Constitutional amendment on membership...
Third Amendment of the Constitution of Ireland - Wikipedia, the free encyclopedia

The State may become a member of the European Coal and Steel Community (established by Treaty signed at Paris on the 18th day of April, 1951), the European Economic Community (established by Treaty signed at Rome on the 25th day of March, 1957) and the European Atomic Energy Community(Euratom) (established by Treaty signed at Rome on the 25th day of March, 1957). No provision of this Constitution invalidates laws enacted, acts done or measures adopted by the State necessitated by the obligations of membership of the Communities or prevents laws enacted, acts done or measures adopted by the Communities, or institutions thereof, from having the force of law in the State.

notes from no w here