Let's talk about responsibility?
The mexicans have clearly identified that american laws are at the root of the mayhem in their country and they have asked the americans to take action
Mexico's president to U.S.: 'No more weapons' - CNN.com
But to take action would violate basic rights, or would it? The US Constitution does not confer a right to traffic in arms but to hold arms. That being so acquisition of arms of any kind for the purpose of resale should be illegal and a purchaser and a seller should be restricted from undertaking such transactions.