The fact that membership in a cooperative arrangement is voluntary, Gruber argues, does not mean that it works to everyone's advantage. To the contrary, some cooperators may incur substantial losses relative to the original, non-cooperative status quo. So what, then, keeps these participants from withdrawing? Gruber's answer, in a word, is power--specifically the "go-it-alone power" exercised by the regime's beneficiaries, many of whom would continue to benefit even if their partners, the losers, were to opt out. To lend support to this thesis, Gruber takes a fresh look at the political origins and structures of European Monetary Unification and NAFTA. But the theoretical arguments elaborated in Ruling the World extend well beyond money and trade, touching upon issues of long-standing interest to students of security cooperation, environmental politics, nation-building--even political philosophy. Bold and compelling, this book will appeal to anyone interested in understanding how "power politics" really operates and why, for better or worse, it is fueling much of the supranational activity we see today.