1. purely algorithmic stable coins (on-chain), such as UST. Voodoo, if you ask me. Can be decentralised.
2. (over)collateralised stable coins (on-chain), such as DAI (not DEI, which is at issue here). Collateralised by other crypto, smart contracts, and what have you. Can still be decentralised.
3. collateralised stable coins (off-chain), such as USDC or (allegedly) USDT. Those are collateralised by good old USD (or treasuries or commercial paper). Those need a central authority that holds on to the USD (or whatever form the collateral takes). So, makes sense that they have TOS.
Tether freezes $150 million in USDT https://cointelegraph.com/news/tether-freezes-150-million-in...
Circle Confirms Freezing $100K in USDC at Law Enforcement's Request https://www.coindesk.com/markets/2020/07/08/circle-confirms-...