  We point out that the $s$-channel unitarity of QCD imposes meaningful
constraints on a possible form of the QCD Reggeon Field Theory. We show that
neither the BFKL nor JIMWLK nor Braun's Hamiltonian satisfy the said
constraints. In a toy, zero transverse dimensional case we construct a model
that satisfies the analogous constraint and show that at infinite energy it
indeed tends to a "black disk limit" as opposed to the model with triple
Pomeron vertex only, routinely used as a toy model in the literature.
