Immigration law refers to the body of law that governs what a person must do to relocate permanently to a particular country. Each country requires temporary or permanent residents to be authorized. In other words, the individuals entering the country must do so with permission, under the bounds of immigration law.
To enter the United States even temporarily, individuals need a passport. Depending on what country the person is coming from, he or she may also need a visa to enter even temporarily. These visas required for short visits are referred to as tourist visas.
When a person wants to stay in the United States longer, he will have to obtain additional permissions. For example, he may need to obtain a work visa. To remain permanently, a green card, resident alien status, or citizenship must be obtained.
Every country has its own visa and passport requirements, as well as its own rules for becoming a temporary or permanent citizen or resident. The laws that determine what a person must do to enter and stay for any given length of time are all set by immigration law rules. These immigration laws can vary greatly; in some places, for example, it is much easier to get citizenship than in others.
Immigration law is normally enforced by a regulatory agency or body vested with the right to make sure the law is being followed. In the United States, for example, Immigration and Naturalization Services (INS) is in charge of making sure immigration law is followed. This involves tracking illegal immigrants as well as ensuring that legal immigrants follow all the rules for becoming residents or citizens.