http://online.wsj.com/article/SB125736987377028727.html

Prohibition has created such enormous profit potential in the underground market that our country’s most remote forests and pristine lands are being invaded by marauders from Mexico bent on cultivating the finest marijuana our gringo money will buy. Mexican workers can earn as much as $2000 per month tending to plots of marijuana in American national parks or Native American reservations. Mexican gang leaders can afford to pay plenty of workers, lose a few plots (and workers!) here and there to law enforcement and the DEA, and still make vast sums of money. Violence on reservations is up, environmental degradation on protected land is up, and, at last glance, those profits…well…yeah…Up!