And we don't usually "do" Advocate Generals' opinions because we don't want to cover too much. But Advocate General Kokott's opinion in Case C-185/07 West Tankers merits reading.
We feared something like this would happen. The Advocate General concludes that the Brussels I regulation (Regulation 44/2001) precludes a court of a member State from making an order restraining a person from commencing or continuing proceedings before the courts of another member State because, in the opinion of the court, such proceedings are in breach of an arbitration agreement.
The practical result, if the Court of Justice agrees, will be that all arbitration of any import will be seated outside the EC. Unless, as the Advocate General points out, the problem is remedied legislatively.
We'll let our friends over at the Conflict of Laws blog comment more extensively.