You might argue this as a theoretical possibility, but it's never going to happen in practice. In practice the trusted entity is always going to selectively allow certain double-spends, and even though it will get caught doing that, people will accept its current revision of the ledger and the world goes on.

For example, the trusted entity might reverse a donation to Canadian truckers due to political reasons (allowing the donator to "double spend" by doing something else with the money later).