Hartford police officers recovered about 400 illegally acquired firearms last year. Those weapons didn't pop up out of thin air. People who owned or had access to legal firearms either lost them or sold them to convicted criminals, the mentally ill and other people who were unauthorized to own guns. Many violent urban crimes and college campus shootings could be prevented if Congress would pass laws to impose foolproof methods of stopping legal guns from getting into the wrong hands. Unfortunately, efforts to pass such laws are often thwarted by the powerful National Rifle Association gun lobby on grounds that...