Overstepping the Bounds: The Implications of UN Security Council Mandate Overextension on International Trust

When the United Nations Security Council authorizes military force through the passage of a resolution, member states are trusted to respect the terms of the given mandate. This thesis asks what happens to that trust when intervening states exceed the boundaries of the provided mandate. I argue that Security Council authorization depends on a fragile, pre-confirmed form of trust (what I term optimism) which member states extend to intervening coalitions before that trust has been earned through demonstrated compliance. Where existing accounts, notably Rathbun's work on generalized trust, treat this disposition as a stable actor-level trait, I argue optimism is relationship-specific and inherently more vulnerable. Extended in advance of proof, it depletes sharply when a mandate is perceived to have been overextended, and this depletion produces observable behavioral consequences for how states subsequently engage with the Council.

I test this argument through two hypothesis pairs (H1A/H2A: overextension erodes trust and produces behavioral change; H1B/H2B: compliance sustains trust and institutional reliance) against two extreme cases of perceived mandate overextension in the Korean War (1950–53) and the Libyan intervention (2011), with the Gulf War (1990–91) serving as a negative case of sustained compliance. Using primary sources including FRUS documents, UN verbatim records, and contemporaneous state statements, I trace observer-state reactions before and after the perceived overextension in each case, alongside subsequent shifts in diplomatic posture and voting behavior.

The evidence indicates that mandate overextension in both Korea and Libya produced measurable trust erosion among a wide range of observer states, from India's post-1950 reorientation toward non-alignment to the post-2011 deepening of BRICS institutional cohesion, while the Gulf War's comparatively faithful execution corresponded with sustained confidence in Security Council-authorized action through the following decade. These findings suggest that mandate compliance functions as a distinct and underappreciated mechanism shaping state trust in multilateral security institutions, with implications for how intervening powers should weigh the long-term institutional costs of operational overreach.