Response of national highest courts to the ECJ's integrationist agenda – Logic behind qualified acceptance of EU law supremacy and direct effect – Several possible explanations for the observed inter-court variation: the courts’ type and organisation; their power to review legislative acts under domestic law; the rules governing access to the judicial forum; the monistic tradition of the legal system and the level of public support for European integration – Assessment of empirical validity of these hypotheses using a new dataset coding the doctrinal positions and institutional constraints of 34 domestic highest courts – Most correlations small – Only one variable – the power to review statutory legislation under national law – appears to have a significant influence on the courts’ doctrinal response to legal integration – Some support for the argument that the varying institutional constraints and incentives under which highest court judges operate shape the way they accommodate and reconcile two conflicting goals