[en] In a framework where massive vector bosons satisfy global SU(2) symmetry and electromagnetic interactions are introduced via W dominance we obtain severe restrictions on the possible W^±, Z⁰ self-interaction terms namely standard anomalous magnetic moments K_γ = K_Z = 1 but quadrupole terms ρ_γ = ρ_Z. The overall consistency of the scheme is explicitly shown. A discussion of the magnitude of the quadrupole parameter is given together with consequences for cross sections and angular distributions in e⁺e^- → W⁺W^- at LEP 200. (orig.)