Immigration law refers to national government policies which control the phenomenon of immigration to their country.
Immigration law, regarding foreign citizens, is related to nationality law, which governs the legal status of people, in matters such as citizenship. Immigration laws vary from country to country, as well as according to the political climate of the times, as sentiments may sway from the widely inclusive to the deeply exclusive of new immigrants.
Immigration law regarding the citizens of a country is regulated by international law. Certain countries may maintain rather strict laws which regulate both the right of entry and internal rights, such as the duration of stay and the right to participate in government. Most countries have laws which designate a process for naturalization, by which immigrants may become citizens.