I've been representing clients in lawsuits to enforce the USCIS Form I-864, Affidavit of Support…
INA §212(a)(9)(A)(ii), 8 U.S.C. §1182(a)(9)(A)(ii)
Once a person is ordered removed from the United States, she is inadmissible to return for 10 years. This becomes 20 years if it is her second removal. “Removal” is the technical term for what most people call deportation. For the visa clientele that we serve, this issue arises very seldom.
Your fiancée or spouse will almost certainly know if she has been previously removed from the United States. The greatest confusion in this regard often comes up when a person was denied entry to the United States at a port of entry (e.g., airport or land crossing). There are two very different things that can occur if someone is denied entry. First, she can be allowed “to withdraw her request for admission.” Basically, the Border Patrol simply allows the traveler to turn around and go home. This is generally what happens, for example, if the person has not secure the proper visa.
The other possibility is far more serious. Border Patrol also has the authority to subject travelers to expedited removal (i.e., deportation). The most common scenario where this occurs is if the Border Patrol believes the traveler is lying to them. In these situations the traveler can be issued a formal order of removal directly at the border.
If your fiancée or spouse was previously denied entry to the United States you need to ensure that she was not subject to expedited removal. You may be able to determine this from her passport, or records she received at the time she was denied entry. But if those do not resolve the issue, you may need to request the entry records from Customs and Border Protection through a Freedom of Information Act request. Such requests are free to make but extremely time-consuming.