Why don't they just ban everything and be done with it?
Some New York City officials have proposed a requirement of a police permit to own an air pollution detector or a geiger counter. Why? Well, if people use them, they might detect something, guess that it was terrorism, and flip out and cause a public panic. Hasn't happened to date, but you never know when it might.
When one councilman asked why groups testing for pollutants in schools couldn't be exempted, the reply was "It becomes a very slippery slope, and it would then be possible for many other entities to sort of drive things through that loophole."
Hat tip to Mechanic...