  The pi-pi scattering amplitude calculated with a model for the
quark-antiquark interaction in the framework of the Covariant Spectator Theory
(CST) is shown to satisfy the Adler zero constraint imposed by chiral symmetry.
The CST formalism is established in Minkowski space and our calculations are
performed in momentum space. We prove that the axial-vector Ward-Takahashi
identity is satisfied by our model. Then we show that, similar to what happens
within the Bethe-Salpeter formalism, application of the axial-vector
Ward-Takahashi identity to the CST pi-pi scattering amplitude allows us to sum
the intermediate quark-quark interactions to all orders. The Adler
self-consistency zero for pi-pi scattering in the chiral limit emerges as the
result for this sum.
