But that's the rub: You can buy and use a device fairly anonymously. Although systems like Thin Thread, as they are described, seem to be able to attack this kind of anonymity, and there are a variety of other attacks possible, that's not the same as a pen register or wiretap, and it takes significant resources to make it work in practice.

4G voice is just data, so that it can be end-to-end encrypted such that, as far as is known, calls can be made secure against any attack. There is no "man in the middle" with access to clear data.

So you say that should not be illegal. Good, so far. But that also means that it is out of reach of law enforcement, and can even be made safe from "rubber hose" code-breaking.

That's what I mean by a stark choice. There is no middle ground. The algorithms exist and that can't be undone. If you put your documents in a safe strong enough to keep a mafia or foreign spy agency out, you can keep anyone out.

Should that be illegal? This isn't just a hypothetical. Any businessman or government worker traveling to places that are corrupt or have repressive governments would be a fool not to guard important documents and communications this well, and the tools are readily available.