Ask HN: As a thought experiment, how would we ban encryption?

I like to sit around and listen to everyone argue about whether encryption should be regulated. I know it's infuriating to some, but I rest assured that, realistically, it can't happen. But can it? How would we go about curtailing the use of encryption technology given that strong encryption tools have already propagated? I think this would be a useful exercise because it shifts the argument from "should we" to "can we." It also forces us to think about the side effects of regulation, e.g., will it have an impact on the competitiveness of individual states that choose to limit cryptography education, practice, and tools?