Isn't a ban on encryption a ban on free speech?
It seems to me that encrypted communication is akin to two people having a conversation in Klingon. If a third party, a police officer, were to interrupt the conversation shouting, "Hey! Speak English! You must be understood!", then that would clearly be a violation of first amendment rights. I cannot imagine a judge would allow the police officer to use a defense of, "Well, they could have been planning terrorism." If the conversation is electronic, and the government does not know what is being said, then it still seems absurd to me for that to be illegal.
Banning encrypted communication is akin to banning all foreign languages, made-up languages, and baby talk. Speak English, little baby, you must be understood or the cops will get you! Absurd.