At Andrew Breitbart's new Big Hollywood blog--
Dan Gifford has "The ‘America Is Arming Mexico’s Drug Gangs’ Lie", an excellent post.
Jeff Jena has posted "Backdooring the Second Amendment" on the same topic.
UPDATE: here's a summary of Mexico's gun laws. Given how strict they are, I'm sure they have no real problems. I mean, unless gun laws don't work or something unbelievable like that.