They think terrorists are too stupid to scout out the subways to see if the cops have put up a checkpoint before taking in anything sensitive. Of COURSE they think they're too stupid to use encryption.
Ah, good. It "doesn't affect you". A perfectly good reason to ban something. Why should you care that not everyone has access to a computer with fast internet at home? You have one, so anyone who doesn't is just out of luck. As long as the law has fixed a non-existent problem with dangerously vague language, all's good in the world.