The
Lisbon Treaty (Article 42) says:
THe UK agreed to the groundwork being carried out for a common defence policy, but all member states had a veto over it being implemented. Nowhere is a "European Army" specified.
There was a document released on the 24th June 2016 on the EU Website. It talks about the common European defence policy, security, and setting nation states budgets from Brussels. The main key words are "ever closer union" and "stronger together". The goal is to bring Defence Policy and Nation state budgets all under one roof, so that the ECB becomes accountable and no future bailouts are required.
The Defence side of it is not getting rid of nation states armed forces, but more creating an EU top command level above Nation state command level, which ensures that if any EU nation state or more than one Nation state comes under threat, the EU can then authorise military action from all Nation states so that everyone is on the same hymn sheet and gives maximum fire power and use of resources.
Effectively, it will overrule Nation states Governments. However that does not effect Nation state governments from standing up their own armed forces for other Operations or exercises (i.e. NATO) outside of the European scope. So not quite an EU Army. It will be similar to NATO, only difference being it only concerns the 27 (at the time) EU Nation states armed forces and has additional powers like overriding Nation state defence policy.
However this is not going by the current act's of the Lisbon treaty, but a step towards a new Treaty, which is likely to take a few more years to ratify.