The possibility of enforcement for the example of PGP encrypted email is pretty obviously real: just throw anyone who is found to use PGP in jail for 10 days.
> Outlawing is a meaningless gesture if the possibility of enforcement does not exist
Irrelevant; it isn't a right if you can't defend yourself in court if you're caught doing it and detecting someone using encryption is not at all difficult. We're talking about rights here, not "what I can get away with". You position isn't defensible.
For that matter, this applies even to granted rights. There are plenty of rights that people have that are outlawed by unenforced (and unenforceable laws). Consider for example laws in less enlightened states that specify what sorts of sex two consenting adults are allowed to have. These laws are not enforced, making them little more than monuments to the ignorance of the past.