I believe the quickest to this mess....is to let the Mexican government file charges on a dozen folks involved. They should demand them to be extradited to Mexico. They might not be able to prove anything with Holder, but I suspect that as a couple of guys arrive in Mexico and get introduced to their version of justice....they will tell the entire story.
I seriously doubt that the President will want to invoke any Presidential power....mostly because he can’t prevent charges from another country coming into effect.