Alright, users and small miners would stay on their old fork, but large miners that control the network would have to comply with the regulations or shut down operations. Eventually users would have to either sell their Bitcoins (sell them on the old or new fork) or switch to and stay on the new regulated fork as well. What's wrong/impossible with this picture I just drew?
I could be wrong, but I would imagine that the coins in the new fork would have lesser value than the old fork. For example, if I have relatives living in a "terrorist" country and the new fork does not allow me to remit them money, why would I even use the new fork?
Well, for starters, let's imagine that 90% of the hashing power (large miners) switches to the new fork to comply with regulations, where would that leave the old fork? It would make each new block arrive in 2-hour intervals, the difficulty retarget would arrive in 2016 blocks in the worst case, that would be 5 months to wait for normal 10-min blocks or even longer (can't remember how much the max retarget downwards in Bitcoin is allowed). Where would that put the credibility of Bitcoin? In short, it would be a total mess.