Planners convened at Northwood, the UK Permanent Joint Headquarters, on 20 April to draft rules of engagement for the 51-nation Hormuz freedom-of-navigation coalition. Washington declined a seat at the table, and Saudi Arabia and the wider Gulf Cooperation Council (GCC) have not signed on.
Both constraints have already been set elsewhere. The Paris posture tied operational activation to whatever ceasefire architecture eventually emerges, with deployment conditional on ceasefire conditions being met. IMO Secretary-General Dominguez's 17 April statement anchored the legal position by surfacing the 1968 tripartite framework the new rules would have to either inherit or override. The Grossi principle from the nuclear track applies equally at sea: enforcement without coastal signatures is rules a boarded vessel's flag-state lawyer can challenge on the Dominguez statement alone.
The practical question Northwood faces is whether a British or French warship can stop a vessel under the new rules without a Gulf coastguard coordinating the stop. Without Gulf signatures the coordination is missing, which means every boarding becomes a bilateral diplomatic event between the flag state and the stopping state. Underwriters will price that friction into hull risk; commercial operators will route around it.
A dissenting read inside European defence ministries is that the absence of US participation is a feature rather than a flaw, because a mission without American framing preserves the European diplomatic space to negotiate with Tehran in parallel. That argument has merit; it also leaves a draft rulebook whose citable authority is currently thinner than the political ambition behind it.
