The historic meeting
Here is a detailed account of the all-night meeting in Brussels Thursday night at which David Cameron reached an impasse with Merkel and Sarkozy (a.k.a. Merkozy) on fiscal union. Since Cameron vetoed the adoption of fiscal union as an amendment to the Lisbon Treaty, the governing law of the EU, the EU countries without Britain instead proceeded to adopt fiscal union via an intergovernmental agreement outside the Lisbon Treaty.
Remember also that the Lisbon Treaty was itself a substitute for the EU Constitution which had been blocked in a French referendum. One way or another, the EU masters get their way..