There is not much the government can do about the sort of terrorist threat that President Obama described in his speech on Sunday. It will always be difficult to stop self-radicalized jihadists, operating under no one's instructions, from carrying out attacks on soft targets too scattered and numerous to secure. The only viable alternative, self-help, is one that Obama seems ideologically incapable of considering. His proposals for new restrictions on firearms move in the opposite direction, based on the assumption that the problem is too many guns in too many hands. Gun control supporters generally dismiss the notion that armed...