A visa is like an invitation into the U.S. An alien who holds a visa to the U.S. must apply for admission at the border of the U.S. When at the border, the alien presents to the border officer his visa issued by the U.S. consulate along with his passport. The USCIS border officers will inspect the alien's visa and passport to determine whether the alien will be admitted into the U.S. If admitted, the alien will be issued an I-94, and a date will be stamped on it indicating the authorized period of the alien's stay in the United States. At that point, the alien attains a legal status to remain in the U.S. (For information regarding the difference between a visa and legal status, please click here). A visa to the U.S. does not guarantee the alien will be allowed to enter the United States for the purpose designated by the visa or any other purpose.

There are two scenarios where an alien with a valid visa can be denied admission into the United States:

Scenario one -Intent of the alien's stay in US is found to be different than the authorized purpose of the visa: When an alien applies for a visa at the US consulate, he applies for a specific kind of visa that covers his intended purpose for visiting the United States. The forms and documentation the alien needs depend on the kind of visa the alien is seeking to obtain. If approved, the alien is given the type of visa that covers the intended purpose of his visit. For example, if the alien intends to visit the U.S. as a tourist, then the alien would obtain a B-2 visa which is the visa issued to tourists. In this case, the alien is given permission to apply for admission to the U.S. for purposes of tourism. When an alien arrives at the point of entry into the United States, he applies for admission to the U.S. with his visa by the border officer who has the power to deny or approve his application for admission. The officer usually asks the alien a series of questions and may inspect the alien's belongings. In our example, upon being questioned, if the alien tells the officer that the intent of his visit is to study, then the officer can deny the alien's application for admission into the United States, and may send him back on the next plane home. In this scenario, the visa would also be revoked because it is deemed to be obtained fraudulently. In this situation, the USCIS's determination is final and not reviewable.

Scenario two - Suspicion that the alien's intended stay in the US is different than the authorized purpose of the visa: In this scenario, the officer does not have concrete evidence as in the last scenario that the alien's intent to enter the US is different than authorized purpose of the visa. AUSCIS officer has the power to deny an application for admission even if his determination is based on suspicion and his evidence for the suspicion is circumstantial at best. For example, an alien attempts to be admitted to the US in New York's JFK international airport with a valid B-2 tourist visa. Upon inspection, the USCIS discovers that the alien has $50,000 on his person. The USCIS border officer concludes, based on the alien's possession of a large sum of money, that the alien intends to do business or to stay for longer than a short period of  time in the United States. Notwithstanding the alien's repeated assurances that he has no intention of doing business or staying for longer than a short time in the U.S., USCIS does not change the ruling. In this instance, the alien can challenge the USCIS officer's decision to deny him admission into the United States. This is possible because the denial is  based on a question of fact or an interpretation of the facts. In the last example (scenario one), there was no question of fact as the alien's intent was clear.

For more information on non-immigrant visa, please click on the following links:
What is a non-immigrant visa?
Who needs a non-immigrant visa?
What are some common non-immigrant visas?
What is the difference between visa and non-immigrant status?
Consulate process for non-immigrants
Entry into the United States
Visa Waiver Pilot Program (VWPP)
Attorney Fees