Onderco, Michal, and Paul van Hooft

Abstract
Informal institutions such as the Proliferation Security Initiative (PSI) have increasingly been at the forefront of global efforts to counter proliferation of weapons of mass destruction. Yet a number of countries with strong non-proliferation credentials and incentives to stop likely proliferators have hesitated to join it. We use insights from alliance theory to explain this counterintuitive situation, and frame the decisions of states that are considering joining the PSI as maximizing between security, autonomy, and influence. We argue that while the PSI and similar institutions are comparatively flexible and less rigid in nature, they also exert a lesser constraint on the more powerful states than do international organizations (IO) which reduce uncertainty by freezing the existing hierarchies in place. We then look at a collection of states that vary in their positions on American hegemony, and find that security interests are predominantly decisive among hegemonic and supporter states and nuclear capable states, which are in favour of supporting the PSI, while counter-hegemonic motivations are largely decisive among states that reject the PSI. Consequently, the perceived lack of legitimacy of informal frameworks by states that are skeptical of US hegemony not only undermines the long-term effectiveness of such frameworks, but also reinforces skepticism of US hegemony. The desirability of increasing informalization of security arrangements should therefore be reappraised in the light of systemic stability.
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