Mariah Carey & Nick Cannon — Mariah Muzzles Nick In Divorce!

EXCLUSIVE

Mariah Carey has gagged Nick Gun – but not in a good way.  He’s not allowed to say boo about their divorce … or else.

Sources accurate to the couple tell TMZ … Nick and Mariah’s lawyers hashed out a confidentiality covenant as part of their divorce … and it’s completely one-sided.  

Nick is barred from saying anything about the split.  If he does, there are severe…