Few rituals are more futile than the "housecleaning" of Mexico's police forces. So deep, broad and brazen is cop corruption south of the border that removing it makes eradicating rats from landfills look easy. Mexico stages quasi-annual purges of officers high and low — last year it was 284 federal police commanders — and yet every year it seems to find itself with an even more criminal constabulary. This year's scandals, however, are especially appalling. Over the summer, President Felipe Calderon's anti-drug czar, Noe Ramirez, resigned abruptly. This week, the likely reason became apparent after Ramirez was detained and accused...