Entering or remaining in the United States without authorization is a civil violation, not a crime. The Department of Homeland Security (DHS) has broad discretion to apprehend individuals it suspects of immigration violations. Individuals may be apprehended at the border, during employment or household raids, as a result of traffic stops by local police, or after having been convicted of a criminal offense.
There are two divisions within DHS tasked with immigration enforcement: Customs and Border Protection (CBP) is responsible for enforcement at the border, and Immigration and Customs Enforcement (ICE) is responsible for enforcement within the United States. If DHS has a reasonable belief that an individual does not have permission to enter or remain in the United States, then that person may be placed in "removal proceedings," which means the government is seeking to deport him or her from the United States.
Individuals apprehended by immigration authorities often do not know what is happening and may not understand what their rights are. Many may accept immediate deportation even though they may not have had an opportunity to consult with an attorney and they may not actually be deportable. A person may be eligible to remain in the United States for a variety of reasons, including a well-founded fear of persecution in his or her home country, having a US citizen spouse, or exceptional hardship caused to his or her US citizen children. Amnesty International has identified more than a hundred cases in the past ten years in which US citizens and lawful permanent residents have incorrectly been placed into removal proceedings.
Individuals subject to deportation still have human rights. International law requires that deportation procedures follow due process and conform to international human rights standards. Like any other circumstance, detention pending removal proceedings must be justified as a necessary and proportionate measure in each individual case, and should only be used as a measure of last resort and be subject to judicial review.