Maybe THAT'S the reason some folks want a fence along the U.S./Mexico border:

To keep us in, instead of the Mexicans out

"Mexico proposes decriminalizing pot and cocaine"
MEXICO CITY (Reuters) - "Owning marijuana, cocaine and even heroin will no longer be a crime in Mexico if the drugs are carried in small amounts for personal use, under legislation passed by the Congress."

And a tip of the hat to "somegirl" at Allspinzone who has some good comments.