Originally Posted by
SomedayRJ
I don't know; ask the FAA. I wouldn't bet my license on it.
I do know that you can't (1) operate an airplane contrary to an ATC clearance and (2) operate an airplane contrary to an ATC instruction except in an emergency. There is a difference, but I would ask the Feds themselves about it.
Does a looming cloud ahead count as an emergency? No, not in my book. Does it require deviation? Yes, if VFR. Does looming airspace ahead that you're not sure if you can penetrate constitute an emergency? No, not in my book. Does it require deviation? Yes.