A U.S. citizen can lose his or her citizenship in one of two ways, by denaturalization (which applies to naturalized citizens only) or by expatriation (which can apply to both naturalized citizens and citizens by birth). Denaturalization takes place when a court revokes the naturalization order because it is found to have been illegally or fraudulently obtained. Expatriation takes place when any citizen voluntarily abandons his or her country and becomes a citizen or subject of another. The Supreme Court has said, however, that the expatriate must have voluntarily performed an expatriating act in order for loss of citizenship to occur (examples are becoming a citizen of another country, serving in the military of a hostile country, or formally renunouncing nationality before a diplomatic officer of the United States).