Entry into the United States is not actually guaranteed when you get a visa. A visa enables you to travel to U.S through air. ( Immigration Court ) In practice, ( Immigration Court ) you would not be able to board a plane en route to the U.S. without a visa. The relationship between Airlines and Customs and Border Protection (“CBP”) determines this. Airlines make sure not to allow anyone travel to the U.S. without a visa.
Occasionally I get questions about what to do when an Airline employee does not allow you to board a plane. The first thing I tell them is that this is not a legal issue. It depends on the Airline and the airport. When you come to the U.S. border, you request a status per your visa from Customs and Border Protection. You get accepted into the country if a status is granted. This is called admission.
In a sense, when thousands of people get their passports stamped at the airport, a legal procedure is completed, and a status is granted. What if you don’t have a valid visa or your requested status is not granted? Your visa might have been revoked without your knowledge.
When you request admission with a non-immigrant visa (e.g. B1/B2 Temporary Visitor or F-1 Student Visa), under U.S. immigration law , you have to prove that you are not an intending immigrant. In other words your visit will be temporary and/or for a specific purpose like studying.
Also there could be an inadmissibility applicable to you. Violation of status is one of them. For instance if it’s deemed that you violated your status in a previous visit by working without authorization, you will not be granted admission.
In these cases, it is not possible for you to enter the country. Your request for admission is not granted. Consequently, your expedited removal is possible. If you apply for asylum at this stage, you will receive a credible fear interview. This interview is very similar to an asylum interview. An asylum officer determines whether you are telling truth or not. Officer also determines whether you have a credible fear.
If you pass this interview, you go through the removal procedures in custody, that is, in Immigration Court which are located within Detention Centers. Immigration Courts work under the Executive Office of Immigration Review, tied to The Department of Justice.
The Department of Justice is a part of the executive branch. Even though they are called courts, technically immigration courts are administrative tribunals. They are court-like institutions that are not a part of the judicial system.
However, “immigration proceedings, although not subject to the full range of constitutional protections, must conform to the Fifth Amendment’s requirement of due process.” 
Removal Proceedings also take place with respondents who are not in custody. There are immigration courts across the country In which Detained and Non-Detained cases are seen. Depending on whether a respondent is in immigration custody or not, their case is placed at Detained or the Non-Detained Docket.
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If a respondent is released from custody through bond or parole, the case is transferred from Detained Docket to Non-Detained Docket Courts. There is a serious backlog of about 900 thousand cases in the Non-Detained Docket.
If you have further questions please contact us to schedule a consultation.
-  8 U.S.C. § 1184(b) https://uscode.house.gov/view.xhtml?req=granuleid%3AUSC-prelim-title8-section1184&num=0&edition=prelim
-  Salgado-Diaz v. Gonzales, 395 F.3d 1158, 1162 (9th Cir. 2005)