Naturalisation is the process by which a non-citizen becomes a citizen of a country. Archives New Zealand holds naturalisation records dating from 1840, although no application files exist until after Aliens Act 1866. The indexes are open, but the actual files are restricted for 100 years from the individual's date of birth, or 40 years from their date of death, whichever is sooner.
An alien in New Zealand before 1914 was merely someone who did not have British citizenship. However large-scale international wars which began with World War 1 in 1914, marked a change in attitudes to many aliens and a change of status for considerable numbers of them. “Enemy” aliens were regarded with considerable suspicion in both world wars. Archives New Zealand holds many alien registration files, which are accessed through various indexes. The index entries are open, but the actual files are restricted 100 years from the date of birth. To obtain a copy of a restricted file you will need to apply to:
Chief Executive and Chief Archivist
Archives New Zealand
PO Box 12050
The Archives New Zealand Citizenship Research Guide can help researchers with this type of enquiry.