The only thing the government can do is impose restrictions on it and prohibit banks from engaging in crypto-related transactions. Despite the fact that India, China, and the United States all have bitcoin restrictions, these countries possess the main crypto exchanges.
Exchanges no dey China (correct me if wrong), Binance, Huobi Global and other exchnago in China then all moved their head quarter from China to another country, when China never even placed total ban on bitcoin and other decentralized currencies. China don ban bitcoin many times but the last ban recently totally ban cryptocurrency mining and transactions (on centralized exchanges), punishment dey for anyone caught making crypto transactions in China.
I like your example, just US that still manage their citizens to trade on certain centralized exchanges that are located in US, no dey difficult for a government to totally restirct any centralized exchanges so their citizens will not be able to access the exchange, or giving the centralized exchange the instruction to disable all Nigeria IP addresses.
We have crypto exchange offices all over the place, and we see advertisements on our televisions every day. Do you think TV stations would accept such advertisements if crypto was banned?
I think we need to emphasize on this, people should try dey differentiate between total and implicit ban, this na where the issue dey come from that some people no still understand.
Implicit banCBN most likely dey involved and not beyond, but citizens can still trade using p2p as CBN ban direct transactions related to cryptocurrencies.
Total banSenators (maybe including House of Representatives) and President support the ban and sign the crypto-ban bill. This will not be what many people would wish for as it go dawn on them. But decentralized option which even dey help privacy and anonymity will be the last resort.