Institutionalism in international relations holds that the international system is not—in practice—anarchic, but that it has an implicit or explicit structure which determines how states will act within the system.

Institutions are rules that determine the decision-making process. In the international arena, institution has been used interchangeably with 'regime', which has been defined by Krasner as a set of explicit or implicit "principles, norms, rules, and decision-making procedures around which actors expectations converge in a given issue-area."

Institutionalist scholars hold a wide array of beliefs stemming from the central proposition that institutions "matter" in answering the question "what explains a particular outcome?". There are four reasons for this:

• They structure choices

• They provide incentives

• They distribute power

• They define identities and roles

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