The "legal" distance varies in different enforcement areas some places 500 yards, some places 150 yards, some places no distance. I can literally anchor my boat 10 feet in front of your blind and set up my decoys. This happened to us once and that's why it's important to remember three sides to every story and that's what the cops and DA have to figure out. Did the old man get threatened or even assaulted by a couple of tough guys? Did the younguns keep sky busting because they wanted to piss the old guy off and he snapped and shot them?
In Currituck county NC you cannot set up a blind without a permit from the "duck commission" and its impossible to get one unless you are a guide or grew up there and you cant set up a scissor rig or boat blind within 1000 yards of a permanent blind ( basically NOWHERE in Currituck sound) so I cant legally hunt a public water/ public resource all in the name of safety cough cough money!
My buddy grew up there and we had 3 permanent blinds but we got tired of replacing them every year cause of hurricanes or Hard NOREASTERs tearing them down only to hunt them once or twice.