A coordinated global effort to restrict or ban Bitcoin would indeed be monumental and likely impossible to enforce. The internet and cryptocurrency technologies are borderless, making it difficult for governments to control or restrict their use.
That will not be impossible. If governments clamp down on all exchanges which allows trade of Bitcoin and impose strict sanctions on anyone caught trading P2P it will reduce the use of Bitcoin significantly. There will be a few channels, which will be termed "black markets" that still allow trades, but not many will want to go down that route as it will be a crime at that time
An isolated restriction by one government will be difficult to enforce but a coordinated approach, which is highly unlikely to happen, will be more successful.
Moreover, attempts to restrict or ban Bitcoin could even have the opposite effect, driving more people to use it as a form of protest or to maintain their financial freedom. This is often referred to as the " Streisand effect" - where attempts to censor or restrict something only serve to draw more attention to it.
Only those who are truly using Bitcoin now to protect their financial freedom will join. Those who are only interested in the speculative value will look for something else to speculate on.
