Citizenship law, also frequently called nationality law, is the body of law that dictates how and under what circumstances an individual may become a citizen of a country. Citizenship law is usually a facet of a country’s statutory code, and is usually implemented through national policies. Citizenship laws attempt to draw a distinction between those who are citizens and those who are not. That distinction is usually critical to other determinations, such as government benefits, tax consequences, and employment privileges.
Citizenship entitles individuals to certain government benefits, but also obligates them to perform duties, like paying taxes or, in some countries, serving in the military. Citizenship law sets the rules for how countries determine who is or is not a citizen, as well as the relevant rules for becoming a citizen. Citizenship laws are not consistent across borders, and each country sets its own rules for obtaining and maintaining citizenship.
In some countries, citizenship laws make clear that all one need do to become a citizen is to be born within the country’s borders. This is typically called “birthright citizenship.” Other countries have more stringent rules. Some countries’ citizenship laws require that a child’s parents be citizens in order for an in-country birth to translate into citizenship, and still others stipulate that citizenship is a factor of not only residence or birth, but also national need. These sorts of countries typically have liberal residency policies, but rarely naturalize immigrants, which would make them citizens.
Citizenship is always a different calculation than residency. A person can be a legal resident of a country for a lifetime without ever becoming a citizen. Citizenship is a particular right that a country will confer on its people as a means of identifying them as its own. It is the role of citizenship law to set the boundaries on how that right is conferred and construed. Citizenship law also sets the rules for permissible dual citizenships, including whether dual citizenship is to be recognized at all.
Policies of citizenship are typically what express citizenship law. Most laws are framed in terms that are subject to legislative interpretation. A country’s legislative body, be it a congress, a parliament, or a national assembly, typically implements citizenship laws through policies that are designed to apply the law in relevant and appropriate ways. This can come in the form of immigration policies, rules on becoming a citizen, the procedures for renouncing citizenship, as well as the standard rights and obligations of citizenship.
There is often an overlap between citizenship law and immigration law. Immigration law focuses on the laws and regulations involved in bringing people legally into a country, while citizenship law dictates what those people’s rights are once in. An immigration law will set the rules for foreigners' entry into a country, while citizenship law sets out the ways through which, if at all, those foreigners can become nationals.