What happens when a eurozone country breaks EU fiscal rules that limit the allowable deficit to 3% of GDP?
Most states have at one time or another broken the limit. France hasn't met the limit since 2007. There has not been a single measure taken by the EU.
The deficit "limit" of 60% is also merely theory, with the EU on average being at 90%. This is of course less realistic to enforce on short notice, but the EU does not even enforce the "60% or decreasing" rule.