While the legal / regulatory aspects (and explicit wording in various regulations) are very interesting, in this case I think it is a moot point.
I am quite sure that never the EASA had contemplated that this incident would happen.
But then if one insists on "what is written" then I ask:
- does EASA have the equivalent that "no-one should fly a plane in a way that puts others in danger?"
- if the claim is that "there was no danger" then I ask, in the event of the 2nd engine inoperative (or some other relevant subsystem failure), has the situation been approved at the airline, and trained for ? Does the Company say in their manual, we can continue to the planned destination ? ( What about other airlines ?)