The Constitutional Charter of the Union of Serbia and Montenegro was finally adopted in January 2003, after protracted negotiations involving unprecedented European Union participation. This paper outlines and analyzes some aspects of the Charter agreement in the context of prospective EU enlargement. It suggests that the EU enlargement context determined the negotiating process and the resulting document to such an extent that, in the end, they came to resemble the EU integration model more than that of state formation or constitutionalization in the classical sense. The EU’s leverage over the negotiating parties was based primarily on the latter’s overriding desire to return to the embrace of the international community. However, the paper goes on to examine in considerable detail the nature and extent of the EU’s involvement in the negotiation process, determining that it was so far-reaching as to call the future viability of the resulting constitutional arrangement into question. Indeed, the paper concludes, the EU will have to be engaged to an extraordinary degree in its day-to-day workings for years to come, to give the nascent Union state even a chance of survival.