Yes I considered that option, but it's mathematically impossible. There's no way to make it so that a general purpose learned mathematical function can't be tweaked downstream to do whatever someone chooses.

So in that sense it's more like the behaviour of the pen and paper, or a printing press, than explosives. You can't force a pen manufacturer to only sell pens that can't be used to write blackmail, for instance. They simply wouldn't be able to comply, and so such a regulation would effectively ban pens. (Of course, there's also lots of ways in which these technologies are different to AI -- I'm not making a general analogy here, just an analogy to show why this particular approach to regulation is impossible.)