Back in the early 70's, backpacking smugglers would try to make marijuana runs from the Nogales area north toward Tuscon.
It was rumored that the Feds had at one time planted cholla to discourage this practice.
Nasty stuff, I watched two hippies sit with needlenose pliars and rubbing alcohol trying to get some cholla out of their stomachs, thighs and pretty much every where else on them.