I used to have a similar problem a few years ago when I was a field tech fixing arcade machines. On of the big accounts we had was running the arcades in motorway service stations and I had to go in once per day and open up every machine and check for coin jams etc.

I really couldn't do this when the place was open so I would pull the shutters halfway down on the front of the arcade (just halfway because they were so incredibly slow to come down) and I would still get at least two people who would duck under and think that it was open for business because they could squeeze inside. I then started to bring down the shutters even lower but I found that so long as there was a gap big enough for someone to squeeze through then they inevitably would.

I ended up just running the shutters all the way down, and at first I would take notice of the people who would come and bang on the them while peering through the gaps and ask me if the arcade was open, and then after a while I just started to ignore them completely. Fucking idiots.