[fancifalmanima]

How does a 3rd party (a court) make that transaction happen without either physically compelling the criminal (not necessarily possible in other countries), or having some kind of master key (which breaks decentralization).

With a bank, they have a financial incentive to stay a part of the international banking system at least.

[alkonaut]

Public and irreversible doesn't have to mean decentralized. The court orders the bank to reverse it on their ledger just like they reverse it today in the accounts - only the ledger requires a public and immutable reversal.