  We study the formulation of the Wilson renormalization group (RG) method for
a non-Abelian gauge theory. We analyze the simple case of $SU(2)$ and show that
the local gauge symmetry can be implemented by suitable boundary conditions for
the RG flow. Namely we require that the relevant couplings present in the
physical effective action, \ie the coefficients of the field monomials with
dimension not larger than four, are fixed to satisfy the Slavnov-Taylor
identities. The full action obtained from the RG equation should then satisfy
the same identities. This procedure is similar to the one we used in QED. In
this way we avoid the cospicuous fine tuning problem which arises if one gives
instead the couplings of the bare Lagrangian. To show the practical character
of this formulation we deduce the perturbative expansion for the vertex
functions in terms of the physical coupling $g$ at the subtraction point $\mu$
and perform one loop calculations. In particular we analyze to this order some
ST identities and compute the nine bare couplings. We give a schematic proof of
perturbative renormalizability.
