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I'm assuming BTCC exchange was a central website?
VPNs can go around such bans, unless the site itself was taken down. You could upload the website on a peer-2-peer HTTPS alternative, such as IPFS.

Internet bans are hard, to be effective you need to take the physical server down. And such actions can be avoided by peer-2-peer. Then a government would have to ban peer-2-peer connections. Those bans can be avoided by VPNs and proxies. And it's practically impossible to ban them, unless you deny access to the Internet itself.

You r right but still it will be illegal

Legality is the politicians opinion enforced by guns.
People will preform agorism as they've always done. Heck, that was why the US was created, the people disagreed with the King's laws.