The contract between Tucker and Fox runs both ways. Tucker's lawyer, Bryan Freedman, is saying FNC is/was under contract not to release any material from behind the scenes showing Tucker in a bad light.
But a lot of shit has leaked. Insiders blame Irena Briganti, in charge of corporate communications, and hated by FNC employee's. After several leaks Freedman threatened to subpoena her communications records and the leaks suddenly stopped. And he has formally told FNC they have to preserve all records related to Tucker.
The Murdochs know that if Tucker gets a rival show he will pull a large crowd....viewers that FNC desperately want themselves. So they are keeping Tucker under contract to keep that from happening.
But the leaks may prove to be their undoing. It's a breach of contract. It's most likely what Tucker's lawyers are working on.