Tactical tragedies: the lone gunman theory of firearm regulation. (Colin Ferguson)

ON TUESDAY EVENING, DECEMBER 7, COLIN FERGUSON SAT WITH WEARY COMMUTERS IN THE THIRD car of the 5:33 train from Manhattan to Hicksville, Long Island. About 6:10 p.m., as the train was approaching the Merillon Avenue station in Garden City, he drew a 9-mm pistol, stood up, and began firing. Ferguson shot 23 people, fatally wounding six, before three passengers managed to subdue him.

President Bill Clinton was quick to take political advantage of what he called a "terrible human tragedy." The next day, during a luncheon with reporters, he cited Ferguson's rampage as evidence of…