  The scattering of longitudinally polarized W bosons in extensions of the
Standard Model with anomalous Higgs couplings to the gauge sector and higher
order $O(p^4)$ operators is considered. The modified couplings should be
thought as the low energy remnants of some new dynamics involving the
electroweak symmetry breaking sector. By imposing unitarity and causality
constraints on $W_LW_L$ scattering amplitudes we relate the possible values of
the effective couplings to the presence of new resonances above 300 GeV. We
investigate the properties of these new resonances and their experimental
detectability.
