  Quantization of systems with constraints can be carried on with several
methods. In the Dirac formulation the classical generators of gauge
transformations are required to annihilate physical quantum states to ensure
their gauge invariance. Carrying on BRST symmetry it is possible to get a
condition on physical states which, differently from the Dirac method, requires
them to be invariant under the BRST transformation. Employing this method for
the action of general relativity expressed in terms of the spin connection and
tetrad fields with path integral methods, we construct the generator of BRST
transformation associated with the underlying local Lorentz symmetry of the
theory and write a physical state condition consequence of BRST invariance. We
observe that this condition differs form the one obtained within Ashtekar's
canonical formulation, showing how we recover the latter only by a suitable
choice of the gauge fixing functionals. We finally discuss how it should be
possible to obtain all the requested physical state conditions associated with
all the underlying gauge symmetries of the classical theory using our approach.
