That law is over 600 years old. Times and facts have changed since then in MC and elsewhere. At that time MC did not have a formal constitution and the ruling house decided itself the matters of succession. 100 years ago MC received its first draft of a constitution which has been modified several times since then (like it has been in many other countries as well). The last modification has been made by Rainier and according to this Alex will not inherit the throne unless there will be another change which is unlikely to happen. I find it unnecessary to discuss those old laws unless for historic curiosity. But they are no longer valid and no judgement will ever be passed on those grounds. No one would want that (otherwise I suppose we would still have heads rolling and hands chopped off in a lot of European countries if judges suddenly decide to have a look back on those old laws
). The last changes were legitimit and legal ad I believe that Alex's rights to succession have been amply discussed in other threads. Besides, if you would start there, then other branches of the family would pop up with their claims, which would be just as legitimate as his. SO until another change will be made, one should just accept the fact, that he is not an heir to throne.