brussels european parliament main brexit coordinator express great concern wednesday talk role eu top court ensure eu citizens right britain brexit stall letter eu brexit negotiator michel barnier guy verhofstadt also say britain ensure common rule northern ireland ireland need physical border two order guarantee coherence integrity eu legal order court justice european union must remain sole competent authority interpret enforce european union law least citizens right provision withdrawal agreement say great concern note negotiations respect stall even progress reverse say talk eu top court role brexit stall eu parliament brexit coordinator