The North Atlantic Treaty Organization is the most robust and deeply institutionalized alliance in the modern world, yet it has faced significant problems in running the International Security Assistance Force (ISAF) in Afghanistan. Specifically, the coalition effort has been plagued by caveats: restrictions on what coalition militaries can and cannot do. Caveats have diminished the alliance’s overall effectiveness and created resentment within the coalition. In this article, we explain why ISAF countries have employed a variety of caveats in Afghanistan, focusing on the period from 2003 to 2009. Caveats vary predictably according to the political institutions in each contributor to ISAF. Troops from coalition governments are likely to have caveats. Troops from presidential or majoritarian parliamentary governments tend, on average, to have fewer caveats, but specific caveats depend on the background of key decision makers in those countries. To demonstrate these points, we first review key limitations facing military contingents in Afghanistan. We then compare the experiences of Canada, France, and Germany and find that our institutional model does a better job of explaining the observed behavior than do competing explanations focusing on public opinion, threat, or strategic culture. We conclude with implications for both research and North Atlantic Treaty Organization’s future.