Chuck Schumer proposes that when prospective military recruits admit drug use in interviews — as Tucson shooter Jared Lee Loughner did — they should be reported to the FBI and entered into the database of people who are forbidden to buy guns. As Schumer points out, it is already illegal to sell a gun to a drug user or addict; this policy, therefore, would make existing law more effective. However, there are several reasons to be concerned. The first is that Americans have a Second Amendment right to own handguns, and this right cannot be denied without due process. Schumer’s...