Do international rules and norms apply to nonstate actors?

The nonstate actors of interest in this article are territorial contenders: political entities that control populated territory, function like sovereign states but are not recognized as sovereign states by other members of the international system. Sometimes they are de facto states, sometimes they are rebel groups, sometimes they are neither of these, instead existing in control of territory with neither conflict against the sovereign state within whose borders they exist nor claims to a state of their own. New data about territorial contenders permit me to evaluate arguments about changing rules and norms in the international system. I find support for claims about the consequences of changing rules about which actors are recognized as sovereign states but not for claims about a norm against conquest after World War II. In the discussion section, I consider implications of these findings for future research.