No one that is drafted in the NBA should be allowed to play college ball even if they were previously an international player.
No one that has decided to play G league ball should be allowed to play college sports.
No one after a certain age, American or international, should be allowed to play college sports. Confirmation of age can be completed by medical specialists that can make an informed decision about a player’s age based upon bone maturation, whether medications have been used to hinder the closure of growth plates, and telomere length among other things that I have not thought of to determine the age of a player.