[mike_hearn]

This is angels-on-pins level stuff, though. In normal English lax enforcement of a rule doesn't mean you're not required to obey it. It just means you're gambling that you won't be put under sufficient pressure to crack your resolve.

All EU countries have to publicly commit to joining the Euro and doing the work to do so. They are therefore required to join it, under any reasonable interpretation of the treaty language. The fact that some countries realized they could just not do what they agreed to and/or hack their economy to avoid the entry criteria, without any consequences, is good evidence that the treaties are indeed meaningless. But lax enforcement isn't the same as no requirement. The EU Commission could change their stance at any time.

[dfawcus]

It is not just down to Commission interpretation.

It has been a while since I last looked at this, but from memory a pre-condition for Euro adoption is spending a certain amount of time within some formal "convergence mechanism", however there is no obligation to join that convergence mechanism.

This could well be ERM-II which I have in mind.

[mike_hearn]

I think you are required to join it, but proceeding to actual Euro rollout requires a currency to be within a certain range for a period of time, and that requires active intervention in currency markets. Governments can just either not do it or claim they can't intervene enough to stay on target.