The one thing that you only implicitly touch upon is the fact that many of these people, regardless of whether they are unwilling or unable, follow their "addictions" (for lack of a better term) to crime. And, yes, you point out that that crime is already illegal, but I think society at large has a responsibility not only to punish and rehabilitate those that commit crimes, but prevent people from commiting them in the first place. Since these sorts of "addictions" are a strong precursor for future criminal behavior, it makes sense to regulate it, in my opinion. That doesn't mean that this particular law didn't go too far, nor that it wasn't created for moral rather than societal reasons.

And, just to be clear, I'm totally on board with the concept that there are redundant laws that make already illegal actions illegal again, and there are laws that make otherwise licit actions illegal solely because of their possibility to lead to illegal actions, and that those laws are, 99% of the time, infringements on civil rights. However, there are occasions when the benefit to society at large has to trump the rights of the individual. I haven't really put a lot of thought into it in regards to gambling "addictions", and, again, I think that this law, at the very least, went way overboard, but I can believe that there are legitimate arguments for restrictions.