The problem, J.J., is that the law (over here anyway) places a great emphasis on what is reasonable. It is not reasonable to expect people to read the criminal code or a list of enforced by-laws before they visit somewhere.
Well, generally, I think it is reasonable, especially with some of things we're talking about, like age of consent.
I live in Gwynedd. My parents live in Shropshire, my sister lives in Cardiff and my brother lives in Nottingham. While legislative differences between localities are less pronounced here than in the U.S, they still exist. I don't think that it's
reasonable to expect me to look up by-laws, council regulations or (in the case of my parents and brother) any differences between the law in Wales and on the other side of the Dike, whenever I visit a member of my family. My brother used to live in Düsseldorf; I never visited him when he lived there, but if I had done it would, perhaps, have been reasonable to expect me to check for any major differences between the law in Britain and Germany but not (I would argue) between Wales and NRW or between Gwynedd and Düsseldorf. "Ignorance of the Law is No Excuse" is mostly just an excuse to boost police conviction rates.
Now, if I were to move to Nottingham (or whever) to set up a business or something (not that I'd ever do that, but this is hypothetical) it
would be reasonable to expect me to know a bit about the differences between by-laws in Gwynedd and Nottingham. But that is
not the same as merely visiting somewhere... or maybe not even the same as living somewhere. Most people don't know all the by-laws that affect the place where they live, do they.