As I was in doubt about this matter I sent a ticket to a national exchange which I'm customer asking if the government could create a law confiscating bitcoins, then the exchange just told me: well, we can't predict what the government will do.
Again I asked them in a hypothetical scenario where the government made a rule like this to confiscate bitcoins, how would the exchange act regards this matter, and they just told me to keep in the platform only bitcoins I use for trading activity and to withdraw the rest of my coins to a safe wallet. That was their recommendation.
After reading the two replies they sent me, a red sign lighted in my head...
That's a good answer, I think governments can't take your coins from your wallet, but they can take it from exchanges. Think about it, if you are dealing with some place that deals with the government, there is always a chance that they can reach it. All they have to do is send a mail about what needs to be done, and if they send one that says "all local exchanges will have to deliver all the coins on their possession to government or it will be punishable by jail" and then what are you expecting these exchanges to do? They will of course deliver and give all the money to those governments.
This is why I think you should keep your coins in a secret hardware wallet, that way you could hide it from everyone. Of course you may want to trade or buy or even have a bit of money there, but do not keep all of it there unless you are using them, if you are not using it, just put it on a hardware wallet.
Indeed, not all of the total Bitcoin in circulation can be confiscated by the government if this program continues. but unfortunately, other forms of refusal still exist, for example all trading sites are frozen by the government so that their very fast movements have to be crippled because they do not have a permit. Bitcoin users will return to like p2p so that all transactions are not detected by the government. This is the worst picture of the government if it legalizes Bitcoin and replaces it with CBDC. But I admit CBDC will not be equivalent to Bitcoin even though the direct government makes it.