This thesis analyzes the challenges presented by ethnic movements in the first world to the sovereignty rights of nation-states. Modern states, that erased the former identities of their native populations, saw with the termination of the Cold War, the resurrection of those past identities, claiming self-determination. Some movements were successful in seceding and establishing new states. Whereas some other ethnic movements reached accommodations with power devolution mechanisms. However those that have not been able to achieve both, experienced continuous ethnic strife in the political sphere. The thesis explores the Northern Irish case as a First World nationalism that has not been able to achieve either. The Irish case is analyzed in order to identify reasons behind the existence and emergence of First World ethnic nationalisms.