The world community makes it impossible to commit such a crime without being caught. With the internet, every one is able to know what is stolen, and anonymity is difficult to have now. It is important for collectors, as well as museums to have good photographic records of their collections to help identify stolen items.
The sentences were too short, but now these people should be know to all collectors and dealers, so they should not be able to sell anything again, not even an old penny.
Best
Gsu