Anyone who is not a U.S. citizen can be removed or deported from the United States, even immigrants who have permanent residence status with a green card. Since September 11, 2001, Congress has passed many statutes broadening the grounds upon which people can be deported. Criminal convictions in particular are grounds for deportation and the Department of Homeland Security is working hard to make sure everyone with a criminal history is deported.
The immigration laws contain long lists of reasons that people can be removed from the United States. One of the most obvious reasons is that the person arrived here illegally, or entered with a visa but then stayed on beyond the permitted time, and thus has no basic right to remain here. Other reasons include things like violations of criminal or immigration laws. (Even forgetting to tell U.S. Citizenship and Immigration Services that you've changed your address is cause for removal.)
Actually, even a U.S. citizen can be deported in rare instances. If the person arrived in the U.S. as an immigrant, but committed fraud in order to get their green card, or during the process of applying for citizenship (naturalization), that person's citizenship could be revoked and the person placed in removal proceedings.
Your first realization that you've got immigration trouble may be your arrest by the immigration authorities (called Immigration and Customs Enforcement, or ICE). This often happens during workplace or other raids.
If, however, you've already been seeking legal status in the United States -- for example, you submitted an application for asylum or a family- or work-based green card, which was then denied -- things won't start out quite so dramatically. You will receive a "Notice to Appear," or NTA, by mail.
The NTA will inform you that removal proceedings have begun and give you a date to show up in court for your "Master Calendar Hearing." During that brief hearing, if you plan to argue your case, you'll be given a date for a "Merits Hearing."
If a person fails to appear at any immigration court hearing, that person will automatically be issued an order of removal and must leave the United States.
You will be given as much time as you need during your merits hearing before the immigration judge to argue your case. (These hearings often run out of time and get postponed to later dates.) With good legal representation, you may be able to show that the immigration authorities made a mistake, or that you have legal grounds upon which to remain in the United States.
An immigration attorney is a vital component to succeeding in a removal hearing. Unfortunately, though immigrants are entitled to legal representation, the U.S. government will not pay for it. You must be able to afford to hire an attorney, or find one who's associated with a nonprofit or charity organization that provides low-cost legal services. (They rarely work for free, since they get no funding from the government.)
A person who is in the country illegally can choose to leave voluntarily rather than fight the deportation. The advantage to this is that you can re-enter the United States if and when you get a proper visa, without being forced to wait several years, as people who were formally removed do. People who are deported cannot re-enter the United States for at least five years, and up to twenty years depending on the reason for the deportation.
A negative decision made at the removal hearing can be appealed to the Board of Immigration Appeals, or BIA. This is done in writing -- you won't need to appear in person, although you can if you wish. (But you'd have to travel to Virginia.) Expect to wait months or years for a decision.
Whether a person is held in custody while awaiting the appeal hearing will depend on whether the person is considered a flight risk.
If the BIA denies your appeal, you can appeal its decision to the local federal circuit court of appeals. This too is likely to take a number of years. Your lawyer will likely have to appear before the court for oral argument. Nevertheless, it's worth it for some immigrants to make this appeal, because they at last succeed with their case.
While an immigrant can appeal a negative decision of the federal circuit court of appeals, it is rarely done. Such appeals are heard by the United States Supreme Court, which takes very few immigration cases.
An appeal at any level will be expensive and time-consuming.