Why Appeals to Complementarity Often Fail to Boost Support for the ICC

📌 Research Question and Theory

Complementarity holds that international organizations (IOs) step in only when domestic institutions fail. Supporters of IOs such as the International Criminal Court (ICC) frequently invoke complementarity to justify international action and to pressure domestic authorities. The central question asks whether appeals to complementarity increase public support for ICC investigations or for domestic investigations.

📋 Large Multi‑Country Survey Experiment

This study evaluates the largest survey experiment on the ICC to date, with more than 10,000 respondents across five countries whose cooperation could be pivotal for the Court:

• Georgia
• Israel
• The Philippines
• South Africa
• The United States

The experimental design tested whether messages emphasizing complementarity—i.e., that the ICC acts only when domestic institutions fail—change public willingness to support ICC investigations or to support domestic investigations prompted by ICC involvement.

🔎 Key Findings

• Evidence that complementarity appeals increase public support is modest at best.
• Effects are heterogeneous: impacts vary across the five countries rather than showing a consistent pro‑ICC boost.
• Complementarity messaging does not reliably increase support for either ICC investigations or domestic probes.
• In some contexts, an IO’s negative judgment of domestic actions appears likely to be perceived as paternalistic and, particularly in Global South settings, as neocolonial.

📣 Why It Matters

• A central legitimating argument for IO action—complementarity—may have limited persuasive power with global publics.
• The findings imply that IOs and their advocates cannot assume that appeals to procedural restraint will translate into broader public backing; such messages may backfire or trigger sovereignty concerns in some countries.

This study preserves the original data and results while highlighting the practical implications for international institutions seeking public support for overlapping international and domestic justice processes.