In other words, leadership fosters legalization—the development of obligatory and precise rules implemented by third parties (Abbott et al. 2000). Leadership may take a wide variety of forms such as advancing a new area of customary law, negotiating a treaty formalizing a previous custom, establishing a new convention, or pursuing judicial rulings to set a legal precedent.

Most notably, we gain leverage over the complex record of U.S. policy toward international law by disaggregating the concept of support along five dimensions: leadership, consent, internalization, compliance, and enforcement. Until recently, research on states’ support for international law focused largely on only two forms—their consent to be bound by treaties and compliance with the treaties they signed. Mark Pollack has advocated the study of two further dimensions of support—states’ leadership in creating international law and their internalization of its provisions into their domestic legal orders (Pollack 2015). We build on Pollack’s four-part conceptualization by adding a fifth dimension: enforcement—states’ efforts to compel other states to abide by international law.

The U.S. relationship with international law is often seen as paradoxical at best, hypocritical at worst. The United States earned a reputation for leadership in international law after World War II, spearheading numerous international conventions and organizations as foundations for international order. Yet despite its steadily growing portfolio of international agreements (Krutz and Peake 2009, 2; U.S. Department of State 2020), the United States has prominently refused to ratify several major conventions that enjoy widespread international support—including some that its own negotiators helped produce. From nuclear weapons and anti-personnel land mines to carbon emissions and war crimes, U.S. leaders have repeatedly invested substantial resources in developing international law only to refuse to subject themselves to it, giving rise to accusations of hypocrisy and imperialism (Angie 2004; Nardin 2005; Monbiot 2012; Denyer 2016).

For example, the United States used financial aid to encourage Ukraine to accede to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1994. When peaceful incentives fail or when the situation is urgent, though, states may turn to more forceful means. For example, the UN Security Council authorized Operation Desert Storm to liberate Kuwait after the Iraqi invasion in 1990, Israel and United States deployed Stuxnet to impair Iran’s nuclear proliferation efforts, and the United

No mere instrument of foreign policy, international law helps constitute states’ identities and interests. Moreover, since moral persuasion is not dependent on material resources, constructivism opens the door for nonstate actors to shape international law on numerous issues, such as human rights (Klotz 1995; Keck and Sikkink 1998; Risse-Kappen, Ropp, and Sikkink 1999), chemical and nuclear weapons (Price 1997; Tannenwald 2007), landmines (Price 1998), and international criminal law (Deitelhoff 2009).

Realism also struggles to explain why the United States has frequently sought to avoid overtly violating international law by pursuing covert interventions, even when doing so assumes greater strategic risk (Poznansky 2020)

Realism thus has little trouble explaining why the United States might back out of international agreements—including those it helped create—if respecting those commitments would not serve its current strategic interests. It can also readily explain why the United States assumed a prominent leadership position in crafting a new international order after World War II, when its economic and military preeminence afforded an opportunity to shape the rules of the international system to best suit its interests moving forward.

Challenging the material ontology and in some instances the positivist epistemology of realism and liberalism, constructivists emphasize the constitutive effects of internationalPage 6 → law on state identities, which interact with international norms to drive state behavior (Kratochwil 1989; Ruggie 1998; Hopf 1998; Checkel 1998).