oh_sigh suggested that we should replace the general duty of a citizen to know the law of the land, with a presumption that if you have a professional license, you are knowlegable of all relavent laws and regulations, and thus cannot clam ignorance to avoid prosecution.

My general claim is that that is essentially already the case. If you become a citizen you have to pass a test to demonstrate familarity with the local society (if you're born here, high school is mandatory). This is no different than how professional licensing works. You could argue that citizenship tests/H.S. barely covers the law, but professional licensing doesn't either. My claim is not that the current system is neccesarily perfect or good, just that the current system where you're expected to know the law is functionally equivalent to expecting professionally licensed people (other than lawyers) to know the law, except that you just have a new class of people who are exempt for roughly no reason. Thus it doesn't really make sense as a suggestion since it is basically what the status quo is.