"Ignorance of the law is no excuse."
We've all heard that saying. It appears in many works of fiction and is often used as a sound bite by judges and prosecutors in real life. I hadn't put much thought in to it until this morning when I read it in an article about people who have been arrested and charged with crimes under wiretapping laws for recording public officials, often police officers, in public.
If a law significantly deviates from what would generally be expected by a lay person such that said person could easily inadvertently violate it in going about their day, as far as I'm concerned ignorance is a completely valid excuse. It's absurd to expect someone outside of law-related fields to even have a rough idea of what laws they may run afoul of accidentally, nor should someone be expected to call their lawyer to see if it's OK before doing something in public.
A great example of this situation handled right is the state of Virginia and their law against radar detectors. It deviates from the national norm, so right after the state line and every so often along the highways you will see signs spelling out in bright reflective letters that radar detectors are illegal in that state. It's a stupid law that should never have existed, but they have at least gone through the trouble to explicitly defeat the ignorance argument.
If you want more, Dumb Laws has a whole collection. Some of these are so absurd it makes one wonder what situation inspired the law in the first place, but some of the others if you had the right combination of officer and prosecutor you could actually be charged with a crime for violating a law that 99.999% of the world would be rightfully ignorant of. Further, as put quite well by Illinois State Representative Chapin Rose, "when you have a law that prohibits something your average Joe thinks is perfectly legal, it undermines respect for the rule of law.”
Ignorance of the law, depending on the situation, should be a completely valid excuse. Beyond that, when legitimate ignorance of a law is even brought in to the discussion it likely means the law itself should be reviewed for change or removal, as it probably is not in favor of the people.