There are not that many laws we agree in advance to obey.
I don't speed when driving, not because I can't, but because I agreed to obey the law in order to get a license, and because I value MY integrity. I don't know why the speed limit sometimes drops at certain places, but I agreed to obey the rules of the road.
A pilot also agreed to obey the law in order to get a license. The law states landing on Pickerel Pond is illegal (I've talked to the State Marine Patrol to confirm this). Thus, the person who lands here is consciously choosing to break the law. I don't even know why the law was made (though I very much appreciate it and am glad for it), but if the pilot doesn't like the law s/he should take it up with whomever made the law, rather than just deciding to ignore it.
NYC decided a few years ago to stop ignoring "minor crimes" like jumping over the turnstiles at the subway and things like jaywalking, all minor stuff. What they found was that the overall crime rate (rape, robbery, etc.) dropped too.
While I never agreed in advance to not murder someone ...
I DID agree to not speed, and the pilot DID agree not to land in prohibited spaces.