If they really are there to "serve and protect", surely they'd provide you with the laws, since you're just trying to be informed as "ignorance is no excuse".
Here is a question. Given the volume of laws at the local, state and federal level, how long would it take a person to read - not familiarize but just read - all the laws from the time they reach the age of majority - lets say 18. Now take the average adult reading speed of about 250 words per minute. Figure an eight hour day - say that instead of being involved in productive labour you just read all the laws. That's 120,000 words per day. Figure about 250 work days per year - five days a week, fifty weeks a year (two weeks off for vacation and potential law-breaking). That leaves 30,000,000 words per year.
The average life expectency is about 77, leaving 59 years to do this in. The average federal registry each year is about 65,000 pages(it varies but that's ballpark.) I dont know the wordcount but figuring it at 250 words per page, that is over 16 million words. Now you might think at this point that it almost seems physically possible. But remember that's only the federal government. Also it's not only the current year's laws but all laws from previous years that you have to adhere to. So each year you spend half your time on the current year and half on a previous. After 59 years, this catches you up to not quite 30 years before your birth. All else is physically out of your reach as you are dead.
Conclusion: It is not
physically possible to familiarize oneself with all laws and regulations, which means that ignorance, while not an excuse, is certainly a fact. A general principle that goes against physical facts can not be adhered to by any sane individual. Ignorance being no excuse is flatly ridiculous on these grounds.