That really might be getting much challenging for you to even judge good standing accounts including green trust. You should simply go through the post on which they recieved merit and judge that post according to your point of view and see if it seems a genuine merit transfer. If you feel anything fishy then you can reject the application maybe.
Even i am confused what can be done against such merit abuse but you are well trained and wise enough to judge peoples so i really hope you undergo this much wisely. I would love to hear your results as it would be exciting for me..