A trade happens only if the seller wants it to happen.The states can try to buy hashpower and coins,but the sellers/miners have the freedom to refuse to sell it.Yes,they could get monetary profit from such deal,but eventually they will lose their business,because of the government control over the hashpower and the majority of coins,which will make a government a monopoly.
Otherwise yes, you have the freedom to refuse it,
but how do you do it, if the government is well pseudoanonymized? That's the core of problem.