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International relations scholarship has long debated whether international institutions genuinely shape the behavior of major powers or merely reflect political interests that already exist. The Nuclear Non-Proliferation Treaty (NPT) is often cited as a case where this debate is especially sharp, since the Treaty lacks binding enforcement mechanisms, leading many scholars to doubt its capacity to influence state behavior. This paper asks whether successful NPT Review Conferences nevertheless function as normative signals that shape subsequent state behavior, even absent formal compliance mechanisms.
The paper argues that successful Review Conferences communicate internationally recognized expectations of cooperation, which can reduce perceived security uncertainty and create conditions under which states adjust defense policy. Rather than treating treaty compliance as a legal or declaratory matter, the paper reconceptualizes it as something observable in behavioral outcomes — specifically, military expenditure. This shifts the empirical question from whether states comply with the NPT to whether institutional outcomes leave a measurable trace in defense policy.
Using a cross-national panel of nuclear-weapon states, alliance-protected states, and non-nuclear states outside nuclear umbrellas, the paper shows that successful Review Conferences are associated with a reduction in military expenditure in the following year, an effect that weakens over longer time horizons. States respond differently depending on their security position, suggesting that institutional signals are interpreted unevenly across the international system rather than producing a uniform effect.
By connecting multilateral diplomatic outcomes to defense spending, the paper contributes to debates on international institutions, security policy, and the behavioral effects of "soft" institutional signals. It suggests that even treaties without enforcement power can shape state behavior by altering expectations about the international security environment — a mechanism that existing compliance-centered approaches to the NPT tend to overlook.