From the Small Wars Journal we have a blog post by a Mr Robert Bunker, "Border Corruption of US Officials by the Mexican Cartels & Cases Shown".
What can I add to what is at the link? Very little. I would note this is why we ended Prohibition. Legalizing drugs won't make the cartels go away, but it will help create an environment in which it will be easier for Federal and State Governments to secure the support of the citizens in fighting this problem and helping those who have been crippled by drugs. And save money in the long run.
Regards — Cliff