Citizenship of the United States
A person who is considered a citizen by more than one nation has "dual citizenship". It is possible for a United States citizen to have dual citizenship; this can be achieved in various ways, such as by birth in the United States to a parent who is a citizen of a foreign country (or in certain circumstances the foreign nationality may be transmitted even by a grandparent) by birth in another country to a parent(s) who is/are a United States citizen/s, or by having parents who are citizens of different countries. Anyone who becomes a naturalized U.S. citizen is required to renounce any prior "allegiance" to other countries during the naturalization ceremony; however, this renunciation of allegiance renunciation of citizenship to those countries.
Dissolution of Czechoslovakia
By contrast, the Czech Republic has formerly prohibited dual citizenship for naturalized citizens, requiring them to give up existing citizenship(s) prior to receiving citizenship of the Czech Republic. This requirement could only be waived if giving up an existing citizenship might put the applicant or their relatives in danger of persecution in their homeland, which was not the case of applicants from Slovakia. This situation changed with the new Citizenship Act of 2013 (186/2013 Sb.), in force since January 1, 2014. However, most Slovak citizens are still unable to become dual citizens of both the Czech Republic and Slovakia, since they automatically lose Slovak citizenship upon voluntarily acquiring another one (see previous paragraph). Exempt from this law are only those Slovak citizens who obtain a foreign citizenship by virtue of marriage with a foreign national. Some Slovak politicians have speculated in the media about softening the Citizenship Act, but no change has yet materialized as of January 2015.