Some potential immigrants are barred from entering the United States. Inadmissible aliens cannot enter the country as immigrants, refugees, or asylum seekers because they fail to meet the necessary requirements. Reasons for inadmissibility include:

• Communicable diseases. Carriers of diseases such as tuberculosis, AIDS, typhoid fever, and other serious ailments that can easily be transmitted are not allowed to emigrate. The reason is obvious: Someone carrying a serious or deadly disease can infect others and create a severe health crisis. (It is possible for someone with a serious communicable disease to have a finding of inadmissibility overturned, but only if he or she can prove that the disease in question has been cured. For some incurable diseases, such as AIDS, a waiver may be granted.)
• Criminal record. Anyone who has committed crimes classified as “aggravated felonies” are generally denied admission to the United States. Aggravated felonies include serious crimes such as murder, rape, and drug trafficking. Other aggravated felonies are treason, espionage, and terrorist activities. (In certain cases, some ex-convicts who seek asylum can get a waiver, but they have to be able to prove to a judge that their crime was not serious or that the charges had been trumped up by their government.).
• Physical and mental disorders. Certain conditions bar aliens from immigrating to the United States, although aliens can try to prove that the condition in question has been cured or is under control.
• Terrorist and or espionage threat. In addition to those who have been convicted of aggravated felonies, anyone deemed likely to engage in subversive activity against the United States will be denied entry.

As covered under the Illegal Immigration Reform and Immigrant Responsibility Act, inadmissible aliens can be deported through the procedure known as expedited removal. Aliens who possess no entry documents or whose documents are either fraudulently obtained or counterfeit are subject to expedited removal. So are aliens who have entered (or attempted to enter) the United States without having first been admitted by an immigration officer at a standard port of entry. Aliens have the right to make claim to legal status in the United States, or they can ask for asylum. While the INS can allow an alien to appear before an immigration judge, there is no obligation to do so, and the alien may simply be ordered removed.