Surely the point should be that whether muzzle up/down or otherwise,.......the weapon must be pointing in a SAFE direction at all times???
If some one is before you, behind you, lying on the floor, up on a ladder or flying on a trapeze.....its the weapon handlers responsibility to ensure it is pointing at nobody at all times.
Well that is our law. It works well when everyone observes it, and those who don't observe it get a well deserved bollocking from whoever else is around at the time. Peer pressure........
Anyone intending to come shoot here in NZ will have to have learned that and passed their basic Firearms safety handling test (equivalent to ours), of which this is a core part. PCP air rifles are now firearms by law here.......and regarded the same as a shotgun/rimfire/Ak47/elephant gun.