When the Transportation Security Administration announced that it will allow passengers to carry small knives on planes effective April 25, my reaction matched that of Rep. Eric Swalwell, D-Calif., who has called the policy change “misguided and, frankly, dangerous.” It’s impossible to think about the ban on knives on planes without remembering what prompted it — the Sept. 11, 2001, attacks. But then I thought, I’m always urging Washington to reconsider regulations that don’t work.