Such sites are generally untrustworthy and often do not update properly, especially in the last 4 years when numerous states have relaxed their knife laws. Though, I would say that knifeup.com does a pretty good job going state by state and is one of the few sites that incorporates case law. Only error I found was a state that had passed a new law 6 months prior that had not been updated.
I would contest that you need a law degree to understand knife laws of most states. I certainly don't have one and I feel I have a very good grasp of nearly every state I've researched. All laws are freely available on the internet from their respective government websites, federal, state, county and city.
But you know one of the most interesting things I've learned over all these years, reading all law books and talking to all those cops and DAs, is that the laws themselves are not really as important as you might think. Ever heard the expression "Don't break more than one law at a time"? Except for New York City, a police encounter over a carried knife alone is unheard of. Every case I find where an arrest is made involves the defendant being a knucklehead and getting the police's attention.