Common sense, mark it well on private property
Here in Texas (and other places) ranchers will sometimes use a small device on the ground that fires a single .22 round straight up with meat or hide as the bait on a wire for coyotes. However, these are usually done with permits, far from humans, and well marked with flash tape etc. So a bow and arrow device pointing straight down from a tree for varmints and well marked to avoid human injuries makes sense to me. Stray dogs chasing livestock on the ranch are always shot on sight anyway, heck we shoot dogs that don't belong regardless of what they are doing.