High courts with abstract review powers to find laws unconstitutional may provide a strong check on other political actors and influence public policy if the judges in these courts are impartial decision makers. This paper tests existing judicial decision-making theories in relation to the behavior of judges on the Peruvian Constitutional Tribunal who are selected exclusively by Congress. Taking advantage of an original data set of judges’ votes on the Tribunal, we find that the origin of the law and whether the enacting governments at the national and subnational levels are still in power at the time of judicial review are important determinants of judicial behavior. Judges’ own political loyalties seem to have no perceived effect on decision making, which suggests that political affiliations are trumped by strategic concerns of judges due to the institutional design of the Tribunal as well as the political context in which it operates.