What CJEU said about ad hoc arbitration agreements in disputes concerning the application and interpretation of EU law

In short, the CJEU held that Member States (i) cannot under any circumstances remove disputes concerning the application and interpretation of EU law out of the EU’s judicial system, and (ii) are duty bound to challenge the jurisdiction of any outsider tribunals as well as the validity of the clause or ad hoc agreement used to submit such disputes to them.