Scholars agree that the preliminary ruling system of the European
Court of Justice has been instrumental in promoting European integration;
however, no consensus has been reached as to why the system is used.
Although many explanations have been posited, there has been no systematic
comparative test among them to date. In this article, we perform this
test. We find evidence that transnational economic activity, public
support for integration, monist or dualist tradition, judicial review, and
the public's political awareness influence use of the preliminary
ruling system.We would like to acknowledge
Matthew Gabel, Eric Reinhardt, Georg Vanberg, and Christopher Zorn for
helpful comments. We would also like to acknowledge the support of NSF
grant #0079084.