As lawmakers in Washington engage this week in moments of silence and tributes to Representative Gabrielle Giffords and the other casualties, they should realize that they have the power to reduce the number of these sorts of horrors, and their lethality. To do so, they will need to stand up to the National Rifle Association and its allies, whose lobbying power continues to grow despite the visceral evidence that the groups have made the country a far more dangerous place. Having won a Supreme Court ruling establishing a right to keep a firearm in the home, the gun lobby is...