[conwaytwitty]

When X is illegal, only the criminals will have X.

Replace X with basically anything.

[biot]

As a mere point of interest, that is logically equivalent to:

  When not only the criminals have X, then X is not illegal.

[lholden]

When X is anything, criminals will likely try using X for bad things. :D

[andylei]

when murder is illegal, only the criminals will murder

[aero142]

"When nuclear bombs are illegal, only the criminals will have nuclear bombs."

I think your grand unifying theory needs more nuance.

[coldtea]

I hope we don't depend on the unavailability of nuclear bombs to the bad guys on them being "illegal".

[aninhumer]

No, we depend on the enforcement of that illegality, which is usually assumed when people discuss banning something.

(EDIT: Previously said "making something illegal", which I realised was ambiguous.)

[marcosdumay]

What, do you plan to make talking about crypto illegal too?

[aninhumer]

I was replying to the general sentiment, not the specific.

Obviously banning encryption is ridiculous, but the "Only criminals will have X" argument is just silly rhetoric.

EDIT: I just noticed the ambiguity you're more likely responding to in my original post. I'll reword it.

[Quinner]

I think your nit-picking needs more thought, nuclear bombs are illegal for an individual to possess, and if someone had managed to obtain a bomb from say the former USSR, they would most definitely be considered a criminal.