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Even if they did, the least they can do is to ban exchange we got these days like Binance, Bittrex, etc. Sites like LocalBitcoins also counts for another and those custodial wallets you know, they're being taxed as well when you cash it out.
However regardless of the bans and efforts they can make, people still have access to VPNs and p2p transaction.
^ Centralized crypto exchanges have been expected that will the first service provider will close if banning crypto or BTC will be implemented. But if you are talking about the BTC banning, the government will not do such a thing, that is their foolish move of they will do that, how they will access the decentralized code that using a blockchain system. People can still access and do buying and selling in any P2P exchnage or even person to person in buying BTC. Nevertheless, I smell the whole world's adoption of BTC, look at those institutional investors now, they are keep coming and invested BTC.