Since the mid-1980s, the Federal Constitutional Court has increasingly constrained the legislative leeway for tax policy-making. This article investigates the causes of the Court’s ostensible judicial “activism” in tax matters. The following analysis of the jurisdiction and its political environment shows that the alleged “activism” indeed exhibits the features of a path-dependent process. Initially, this evolution was far from inevitable but it became increasingly entrenched in the process. Precedence and co-ordinated law-suits acted as positive feedback, while the new case-law was all but impossible to revise by law-making or further litigation. Constitutional tax jurisprudence became “locked in”.