Newly-released documents show that last February, on an official visit to Mexico, Justice Department official Lanny Breuer suggested fighting arms trafficking by using the tactic of intentionally letting guns flow into Mexico via criminals. According to the documents, Assistant Attorney General Breuer suggested the U.S. and Mexico consider working together to allow arms traffickers for Mexican drug cartels "to cross into Mexico," so that Mexican authorities could later prosecute and convict them. The documents indicate Mexico's then-attache spoke against Breuer's idea. He "raised the issue that there is an inherent risk in allowing weapons to pass from the US to...