The ECJ doesn.t enforce but resolves issues of law when they are either unclear or are disputed. The ECJ has no means to enforce. The NAA enforce the law through the national courts: in the UK the magistrates courts up to the Supreme Court.
I would hope that we will not go back to pre 2003 the world has moved on. Hopefully in the upcoming weeks some level of mutual recognition will be achieved. It is too early to say what the final outcome will be. The gloom and despondency that is being projected by some is unjustified.