In the US at least, I beleive the current legal definition is 500 ft in uncongested areas and 1000 ft elsewhere. Above that is considered "public highway" in federal law.
I think there may have been one or two other--possibly state level--cases. It's pretty ambiguous but loose consensus seems to be that you probably have property rights up to 400-500 feet. On rural land, a drone at 50 feet would seem to be fair game for skeet practice.