Why doesn't Mexico hire PMCs or other paid soldiers to fight cartels?

After an extensive week long research project followed by a speech and 12 page paper over private military companies and mercenaries I have found how effective they are when paid to fight. Now seeing how Mexico is incapable of defeating the cartels singlehandedly -- why don't they just get some paid mercenaries to help them finish them off. With their military training and unrestricted ways of fighting it seems they could easily kill and undermine the whole drug business. It only took a few hundred Executive Outcome mercenaries and 9 days to push RUF rebels into the woods and get back lost diamond mines in Sierra Leone, and Blackwater showed domination in Iraq. As well as countless other wars that mercenaries have dominated in. Unconventional yes, but if they worked with Mexico's army and eliminated the cartels one by one it seems to me as if they could get rid of them and regain control, and give peace to their country. Just a though, don't bash.