Yes, but it should be an excuse, and it used to be an excuse. The law is so vast, and subject to interpretation, and subject to which side throws the most money at a court case, that it is literally unknowable. You'd need to merge your mind with computer technology and become a cyborg capable of continuously processing all possible actions you're about to do, to cross reference them with huge numbers of volumes of law books and court cases interpreting them. And, if someone actually did that, the cyborg would probably see all the inconsistencies and then be unable to do any actions and just shut itself down.
Ignorance is a perfectly good excuse for violating any kind of malum prohibitum law. The only laws that I could confidently hold someone responsible for violating would be those that have an actual victim. (Sorry no, it's not an argument that you didn't know theft was illegal.... that you're expected to know.)
As for this poor guy, he may or may not have known what the law was, but likely didn't understand the seriousness of the punishment if caught violating it.