For example, an alien hoping to work temporarily in the United States as a registered nurse needs an employer's petition to obtain an H-1A visa. Similarly, an alien planning to study at a university must present proof of acceptance at the university for an F-1 visa. In all cases, consular officials make the final decision. Generally, no judicial review is available. Once admitted into the United States, aliens are inspected by INS officers, who give them a form I-94 indicating the length and terms of their stay.
Most aliens ultimately return to their country of origin.
Some wish to stay and immigrate. To qualify, the alien must have been inspected and admitted or paroled into the United States, and must meet standard eligibility requirements for obtaining an immigrant visa, and an immigrant visa must be immediately available at the time the application is filed. In addition, the alien must not have been in an unlawful status or, with few exceptions, have accepted any unauthorized employment. The term numerical limitation means several things. First, it refers to the overall limits on immigrants set by Congress.