The reason Holder wanted to get to the guys at the 'top' of the cartels, is so he could make a deal with them.
Obama and Calderon had already met and agreed that they could not control the cartels, and were taking lots of collateral damage.
Areas along the Arizona border have already been ceded to the cartels. There are even signs up stating so.
How do you get the big guys to out themselves? Surely not by telling major gun shops to wink.