  Further developing ideas set forth in \cite{KLL}, we discuss QCD Reggeon
Field Theory (RFT) and formulate restrictions imposed on its Hamiltonian by the
unitarity of underlying QCD. We identify explicitly the QCD RFT Hilbert space,
provide algebra of the basic degrees of freedom (Wilson lines and their duals)
and the algorithm for calculating the scattering amplitudes. We formulate
conditions imposed on the "Fock states" of RFT by unitary nature of QCD, and
explain how these constraints appear as unitarity constraints on possible RFT
hamiltonians that generate energy evolution of scattering amplitudes. We study
the realization of these constraints in the dense-dilute limit of RFT where the
appropriate Hamiltonian is the JIMWLK Hamiltonian $H_{JIMWLK}$. We find that
the action $H_{JIMWLK}$ on the dilute projectile states is unitary, but acting
on dense "target" states it violates unitarity and generates states with
negative probabilities through energy evolution.
