We study the formulation of the Wilson renormalization group (RG) method for a non-Abelian gauge theory. W e analyze the simple case of SU(2) in which the Lagrangian at the ultraviolet cuto 0 contains nine relevant couplings, i.e. parameters with non-negative dimension, while the classical theory contains only one coupling g. W e show that both the physical parameter, i.e. the coupling g at the subtraction point , and the local gauge symmetry can be implemented by suitable boundary conditions

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... r the RG o w. This procedure is similar to the one we used for QED with two crucial new points: the non-linearity o f the Slavnov-Taylor (ST) identities and the presence of two couplings with nonnegative dimension absent at tree level. 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 and perform one loop calculations. In particular we analyze to this order some ST identities. We give a s c hematic proof of perturbative renormalizability.