  In the Wess-Zumino gauge, supersymmetry transformations become non-linear and
are usually incorporated together with BRS transformations in the form of
Slavnov-Taylor identities, such that they appear at first sight to be even
non-local. Furthermore, the gauge fixing term breaks supersymmetry. In the
present paper, we clarify in which sense supersymmetry is still a symmetry of
the system and how it is realized on the level of quantum fields.
