[Cederfjard]

Just because you hide a big bag of cash where no one can find it, it doesn’t necessarily mean it’s yours, just that you have it.

If the US government says that it has lawfully seized your bitcoin, then by law the US government owns the bitcoin, even if they don’t possess it. If you’re successfully keeping it from them, they can and will punish you for it. Again, as FormerBandmate said, that’s the basis of their power.

[once_inc]

As another comment here notes: there is a different meaning behind the words 'seize' and 'control' when used by the government. Seizure doesn't equate control, and in the case of Bitcoin private keys, this difference is significant.

[DocTomoe]

Think of it this way:

A state actor has identified funds on a offshore bank account that they do not have a controlling access to. They did seize a computer that has been used in the past to access that bank account.

The bank accounts owner (or an associate) removes funds from that bank account. The state actor acts as a petulant child and claims by seizing the computer, they also seized the bank account's content - and then proceeds to arrest the bank account owner (or their associate).

No judge in their right mind would let that fly.

[hef19898]

In your example, no, the account owner wouldn't have a right to remove the money if the account and not the computer holding the password, was legally seized by the government. The government so cannot use those funds as they please neither until a legal decision allows them to do (RICO maybe, or anti-Mafia laws in Italy allow for that after court decisions). Also in your example, the bank in a different jurisdiction will get requests from the government in question to freeze the account, which might or might not be followed through depending on bi-lateral agreements and which country is asking on which basis for the account being freezed.

I have no idea why crypto would be treated any different.