Mariah Carey has gagged Nick Cannon -- but not in a good way. He's not allowed to say boo about their divorce ... or else.
Sources close to the couple tell TMZ ... Nick and Mariah's lawyers hashed out a confidentiality agreement 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 financial penalties. But Mariah has the right under the agreement to announce the split on her terms.