or in a tough spot
I think in that situation you do what is possible and sort out the legalities/paperwork later! I know an instance where an AS332L on a UN contract in Sierra Leone carried out a single engine departure from the field, with some very grateful pax who had just been chased through the bush. The crew heard their frantic radio calls and started up in readiness for their arrival, but couldn't start one engine (can't remember now whether it wouldn't start, or it was considered more prudent to just go anyway!)