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.)
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.)