The use of discriminatory behaviors against members of employee representation bodies to combat co-determination is by no means a new issue regarding the discrimination of works council members. However, the prohibition of discrimination based on union membership has hardly been addressed in German labor law scholarship to date. This dissertation therefore contributes to the legal-dogmatic clarification of this issue, the resulting prerequisites and legal consequences, as well as possibilities for further development of discrimination protection. In this context, not only national law is considered, but particularly labor international law is used as a source of insight.