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.
New Zealand nationality law
New Zealand has permitted dual or multiple citizenship since the creation of New Zealand citizenship on 1 January 1949, although dual citizens who actively acquired or exercised their other citizenship could lose their New Zealand citizenship if their continued citizenship was judged "not conducive to the public good". The modern wording is similar; dual citizens may lose New Zealand citizenship by acting "in a manner that is contrary to the interests of New Zealand". A New Zealand citizen who holds another citizenship may renounce their New Zealand citizenship (see below), although this may not be registered if they reside in New Zealand or the country is at war.