  We study the Slavnov-Taylor Identities (STI) breaking terms, up to the second
order in perturbation theory. We investigate which requirements are needed for
the first order Wess-Zumino consistency condition to hold true at the next
order in perturbation theory. We find that: a) If the cohomologically trivial
contributions to the first order ST breaking terms are not removed by a
suitable choice of the first order normalization conditions, the Wess-Zumino
consistency condition is modified at the second order. b) Moreover, if one
fails to recover the cohomologically trivial part of the first order STI
breaking local functional, the second order anomaly actually turns out to be a
non-local functional of the fields and the external sources. By using the
Wess-Zumino consistency condition and the Quantum Action Principle, we show
that the cohomological analysis of the first order STI breaking terms can
actually be performed also in a model (the massive Abelian Higgs-Kibble one)
where the BRST transformations are not nilpotent.
