  We present a method for constructing parent Hamiltonians for the chiral spin
liquid. We find two distinct Hamiltonians for which the chiral spin liquid on a
square lattice is an exact zero-energy ground state. We diagonalize both
Hamiltonians numerically for 16-site lattices, and find that the chiral spin
liquid, modulo its two-fold topological degeneracy, is indeed the unique ground
state for one Hamiltonian, while it is not unique for the other.
