Immigrants have legal rights, duties and obligations of aliens in the United States. These rights are in many respects different from those of citizens. These are the avenues through which an immigrant alien can eventually become a naturalized citizen of the USA with full fledged rights of citizenship.
The Immigration and Nationality Act (INA) was amended from time to time to stop illegal immigration and to make matters easier for legal immigrants.
The congress passed the Immigration Reforms and Control Act (IRCA) of 1986, which shut out illegal immigrants from the benefit of federally funded welfare schemes, strengthened criminal sanctions against employers who employ them and also regularized the status of some of these illegal aliens under an amnesty program.
Aliens with visas can lawfully enter the USA and enjoy freedom from official restraint.
However, in spite of visa the Immigration and Naturalization Service (INS) can exclude an alien from entry into the USA upon landing on the grounds of crime, health, national security and so on. In practice such exclusion is a daily occurrence.
Such excluded aliens can seek redress of their grievance in an exclusion hearing, where the burden is wholly on the alien to prove his right of entry into the US. In some cases the authorities give the excluded aliens asylum or refuge for political reasons. Other excluded aliens seeking to cross the border are lodged in detention facilities until their hearings are over.
INS officers can selectively at their discretion release an alien on parole when his case is pending review. Parole is a limited leave of temporary duration to such excluded alien to move on from the border and detention facilities for the time being for good reasons, such as preventing separation from his family etc.