On 1st April 2009, the Czech Minister for Justice signed the Convention on behalf of the European Community (see the proposal to do so here). Negotiations on the Convention at the Hague were carried out ostensibly under shared competence between the EC and the Member States, but in the wake of Opinion 1/03, of course, the Community has exclusive competence to ratify the Convention. In other words, it does not need to be signed by the Member States (i.e. we’re stuck with it, whether we like it or not.) Denmark, however, will not be bound.
You will remember that Mexico and the USA have already signed the Hague Choice of Court Convention, and with the EC joining that exclusive club only one more ratification is needed for the entry into force of the Convention. My attention has been drawn to the fact that the above statement is vague at best, and misleading/confusing/wrong at worst. Apologies; allow me to rework: the Hague Convention requires two ratifications or accessions to enter into force (Art 31(1)). So far, only Mexico has acceded to the Convention, and no State has ratified it. If either the EC or US ratify it (having already signed it), or a non-signatory State accedes to it, or another Hague member state signs and ratifies it, then the Convention will enter into force (thanks Andrew and Ralf.)
(Many thanks to everyone who emailed/commented to let us know; much appreciated.)