In the wake of the Eurozone sovereign debt crisis, the European financial authorities announced last November that all Eurozone sovereign bonds issued after mid-2013 must contain an identical collective action clause (CAC) in order, if necessary, to facilitate a restructuring of those instruments. 

CACs in sovereign bonds have been the subject of considerable attention over the last ten years. They were introduced into sovereign bonds governed by U.S. law only in early 2003. Yet a surprising number of versions of the clause can be found in modern sovereign bonds. 

The history of the research and development of this contractual provision is, or at least ought to be, relevant to the drafting of the model European version of the clause.

Lee C. Buchheit & G. Mitu Gulati, Drafting A Model Collective Action Clause For Eurozone Sovereign Bonds, 6 Capital Markets Law Journal, 317–325 (2011).