Under U.S. law...
The FAA requires that the commander ensure, at all times, the aircraft will be able to maintain adequate terrain clearance during all phases of flight, both with all engines operating, and with one engine inoperative. This, of course, includes takeoff, climb, cruise, descent, landing, and missed approach. This is the regulation....
Good luck with using your ingenuity when XXXX happens at the worst time.
Fly safe,
PantLoad