the smart contract has a blacklist flag that can be activated by the Tether, this prevents on-chain transfers.
https://etherscan.io/token/0xdac17f958d2ee523a2206206994597c...
The USDT will be burned and the USD released to the rightful owner after law/legal approval -- https://twitter.com/paoloardoino/status/1425188386034311168