BRUSSELS, June 9 -- The statement lasted less than a minute at the podium, but it carried the full weight of what the European Union cannot do. Anouar El Anouni, the European Commission's foreign affairs spokesperson, urged Yemen's Ansar Allah movement Tuesday to avoid any action that would "further jeopardize the chances to reestablish regional peace" - a formulation so carefully hedged it bordered on self-parody, delivered the morning after the Houthis formally entered the Iran war and threatened to seal the Bab al-Mandab Strait.

Brussels has watched this moment arrive for months. Since late April, Houthi officials have issued graduated warnings that the narrow passage between Houthi-held Yemen and Djibouti - through which roughly 12 p...