Naturalization
Naturalization is the acquisition of a nationality or a citizenship by an individual who does not own it by birth. Naturalization is in principle a sovereign act of the State granting it. The criteria which the candidate for naturalization must fulfill are defined in national law, sometimes in a bi-or multilateral treaty. He must generally prove a minimum length of stay in the territory of the State whose nationality he is applying for and be registered as a permanent resident. Some States do not allow dual citizenship and therefore require them to renounce other nationalities and / or citizenship they possess at the time of naturalization. Arrangements sometimes exist for naturalisations by marriage.