We would use bitcoin cash

srsly tho, bitcoin is made for exactly that scenario eh. Imho no one made it legal and no one can make it illegal. It´s there now whether authorities like it or not. (if you think FUD is bad in forums, think of stiff old politicians getting a grasp of what bitcoin does xD)
Also, since it isnt really adopted that widely yet in most countries i dont think ppl would really care or know if banned or not. Doing banned things with bitcoin is what it gave it its value.
i think a ban could make it even more popular xD just like people went to buy guns after sandy hook incident...

just my 2 cents