Posted workers may not generally challenge administrative decisions about which social security law applies to them in the courts of the state of destination. This lack of jurisdiction is all the more problematic as such decisions are regularly made without checking whether the conditions for being posted are actually fulfilled, and judicial protection in the state of origin is found wanting. These weaknesses in the administrative and judicial enforcement of the posting rule facilitate non-compliance, enabling employers to choose a relatively cheap social security system. Such social dumping affects workers, competitors and social security systems. Despite recent ECJ case law on fraud, all too often administrators bind judges rather than the other way around. This article proposes a rethinking of adjudicative jurisdiction.