That's the title of a new paper, co-authored with Martin Gelter, available here. The abstract reads:
The theoretical arguments in favour and against citations to foreign courts have reached a high degree of sophistication. Yet, this debate is often based on merely anecdotal assumptions about the actual use of cross-citations. This article aims to fill this gap. It provides quantitative evidence from ten European supreme courts in order to assess the desirability of such cross-citations. In addition, it examines individual cases qualitatively, developing a taxonomy of cross-citations based on the degree to which courts engage with foreign law. Overall, this article high-lights the often superficial nature of cross-citations in the some courts; yet, it also concludes that, by and large, our analysis supports the use of cross-citations: it does not have the pernicious effects sometimes suggested by critics of the practices, such as undercutting national sovereignty and the legitimacy of the legal system. At best, cross-citations provide a source of inspiration how to interpret national law. At worst, they are largely ornamental and marginally help to make a particular policy argument appear more persuasive.