IME the threat of penalties imposed by the judicial system are nowhere near as effective, as those imposed by mother nature herself.

One of the facilities where I worked experienced drownings every year--in areas clearly posted "no swimming". The facility was over-utilized and under-staffed and those signs meant nothing, if there were no staff attendant to the sign. When I thumbtacked a snapshot of myself, holding a three foot rattlesnake at a shoreline--which could have been THAT shoreline, illegal swimming dropped off to nothing.
A few years later, at another facility, I found that littering blue gloves and wadded gauze, in the access point of a "closed area", kept the area clear...