Constitutional courts (CCs) in federal and quasi-federal systems are often expected to act as neutral arbiters in conflicts between levels of government. This article challenges that assumption by analysing the behavior of Spain’s Constitutional Court over four decades of constitutional litigation. Drawing on an original dataset of 1,888 rulings on all challenges to national and regional legislation (1981–2023), we examine how judicial outcomes are shaped by political alignment, institutional design, and court ideology. Our analysis reveals a consistent pattern of deference to the central government, especially when the Court is ideologically conservative or aligned with the federal executive. These results support a strategic model of judicial behavior and raise broader questions about the role of CCs in multilevel systems. Rather than acting as counter-majoritarian forces, courts may reinforce central dominance in center–periphery conflicts, limiting their capacity to protect territorial pluralism in practice.
