Thanks for that clarification. My apologies. I believed ICE was responsible for things crossing in at the border, and Mexican authorities would be responsible for keeping contraband out of Mexico.

Edit to add: I shouldn't have described that last type of operation then and I apologize for doing so. I'm still confused on how DHS could be blamed for this though, unless the argument is that they should have been inspecting vehicles leaving the country for illegal weapon supplies. Shouldn't their resources be focussed on contraband coming into the US?