Recent scholarship in security studies has started to explore the causes and consequences of various forms of national restrictions in multinational military operations (MMOs). This article makes a conceptual contribution to this literature by developing a theoretical framework of national restrictions in MMOs that distinguishes between structural, procedural, and operational restrictions. I argue that these types of restrictions are governed by different causal mechanisms. Structural restrictions are relatively stable over time and effect deployment decisions irrespective of other factors. Procedural restrictions, on the other hand, can constitute veto points against deployment only in combination with distinct political preferences. Finally, operational restrictions directly affect the rules of engagement of troop contributing countries. The article illustrates the three types of restrictions and their interaction with empirical examples from a range of countries and sketches their impact on MMO deployment decisions and mandates. KEYWORDS Alliances; caveats; domestic politics; institutional constraints; parliamentary war powers; veto points During the Iraq War, Japan's conservative government under Prime Minister Junichiro Koizumi faced severe constitutional obstacles with its aim to make a military contribution to the U.S.-led invasion. In Afghanistan's International Security Assistance Force (ISAF) mission, the German Bundeswehr operated under caveats that prohibited it from joining its coalition partners in the full range of operations by the North Atlantic Treaty Organization (NATO). When chemical weapons were used in Syria in 2013, the British House of Commons effectively vetoed Prime Minister David Cameron's proposal for military action. These examples illustrate how national regulations and conventions can affect democratic decision-making on war involvement and the behavior of the armed forces in the field. 1