The laws are there, Lucas just shot himself in the foot because he never made up a contract whereby he would retain ownership of the work. Whenever someone makes a deal for a film it comes with a contract--when I worked in the camera department I had to fill out a 10-page deal memo every time I joined a crew. If you go under the table like Lucas did, you void any rights you could have demanded the employee give you. Lucas obviously didn't care at the time, because he couldn't forsee the film being successful firstly and prop replicas becoming a market secondly; the trade off, though, is that if the film is so successful that this becomes a market then it means you are making a million dollars on a hundred other things, so its all peanuts anyway. The cost of Lucasfilm's legal suit is probably more than this single man would have made in profit anyway.