Liberalitarians and Hippies hardest hit.
Unfortunately, there is so much money to be made in drugs that there are bribes paid to officials on BOTH sides of the border (meaning, the US Border Patrol isn't lily white, either).
But, yes, Mexican soldiers (paid very well by the drug runners) have used humvees to escort drug couriers as much as five miles into the USA; and nobody wants to take on their firepower (or create an international incident).
But one of these days, something will end up happening (meaning: shooting), and then everyone will regret not
doing something about this earlier, before there was violence.
Lord knows there's no other drug on Earth that handles acute or chronic pain.