That's actually pretty cool and scary at times because it can help deter the criminal activity in the cryptospace but at the same time when being held by a nefarious hands, this way of seizure could mean that any user in cryptospace is going to be on the cross hairs of that entity and it's only a matter of time.
Wonder what cryptocurrency the hacker really used.
It's actually foolish to do that on Bitcoin, seeing how transparent the network is. And I expect the Bitcoin Network participants to be able to handle the issue successfully without breaking the network rules. If the ransom was paid in something else like physical currency or gold, it would be more difficult to trace and retrieve compared to doing so on a transparent currency like Bitcoin. The activities of security agencies on the network has to be transparent too or atleast immutable for the sake playing according to the rules and accountability. Bitcoin makes it easy for the security agencies , so it's important they reciprocate by being accountable.
Was the private keys really retrieved? I'm interested to know how they did it.