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 (established by Treaty signed at Rome on the 25th day of March, 1957).That went into force in 1972 and, as the text clearly shows, made European law supreme over Irish national law. That is no customs union; it is an empire.
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.
That only points to the desire of Ireland at the time to integrate tighter. I agree, however, that at some point in the 70’s the EU had ambitions far beyond a customs union.
Empires are monarchies that rule over many diverse nations. The EU is a multi-ethnic bureaucracy, not monarchy. It will therefore, follow a path of self-destruction typical for bureaucracies as the bureaucrats learn to gratify themselves at the expense of those who work for a living. Further, a monarchy has a unifying idea that attracts nations (for example, industrialization, social justice or Orthodoxy). The EU does not have that, beyond some cheap platitudes.