Serendipity and Wikipedia led me to this a few minutes ago; Niven's Laws, with commentary, January 29, 2002.
4) Giving up freedom for security has begun to look naive.
Even to me. Many of you were ahead of me on this. Three out of four hijacked airplanes destroyed the World Trade Center and a piece of the Pentagon in 2001. How is it possible that those planes were taken using only five perps armed with knives? It was possible because all those hundreds of passengers had been carefully stripped of every possible weapon. We may want to reconsider this approach. It doesn't work in high schools either.