  In this paper, we examine the CP-violating term of the Euler-Heisenberg
action. We focus in the aspects related with the generation of such a term from
a QED-like model in terms of the effective action approach. In particular, we
show that the generation of the CP-violating term is closely related with both
of vector and axial fermionic bilinears. Although, these anomalous models are
not a "viable" extension of QED, we argue that the CP-violating term in the
photon sector is obtained only from this class of models, and not from any
fundamental field theory.
