R eports of alien minors being separated from their parents at the U.S. border—either when they have presented themselves at a port of entry to claim asylum or when they have been apprehended by authorities after unlawfully entering between ports of entry —have raised questions about the authority of the Department of Homeland Security (DHS) to detain families together pending removal proceedings. The Immigration and Nationality Act (INA) does not provide a specific framework for the detention of alien families during the removal process. Much of the governing law stems from a binding, 20-year-old settlement agreement ( Flores Settlement) between the federal government and parties challenging the detention of alien minors, which the U.S. District Court for the Central District of California entered in a case now called Flores v. Sessions . The Flores Settlement establishes a policy favoring the release of alien minors, including alien minors accompanied by an alien parent, from immigration detention and requires that those alien minors who are not released from government custody be transferred within a brief period to non-secure, state-licensed facilities. According to DHS, few if any such state-licensed facilities capable of holding minors and adults together exist. For that reason, it is DHS's position that, to comply with the Flores Settlement, it must choose between (1) releasing the family together and (2) releasing the alien child while the adult family members remain in detention until removal proceedings have concluded. Recent federal court decisions cast doubt on the legality of the second option, however, leaving the general release of family units together as the only clearly viable option under current law. In an executive order issued on June 20, 2018, President Trump directed DHS "to the extent permitted by law and subject to the availability of appropriations, [to] maintain custody of alien families during the pendency of any criminal improper entry or immigration proceedings involving their members." The executive order also directed Attorney General Sessions to ask the district court overseeing the Flores Settlement to modify the agreement to allow the government to detain alien families together throughout the duration of the family's immigration proceedings as well as the pendency of any criminal proceedings for unlawful entry into the United States. While that motion was pending, in a different lawsuit, Ms. L. v. ICE , challenging the government's policy of separating alien children from their parents when family units entered the United States at or in between ports of entry, a district judge issued a preliminary injunction mandating alien family reunification. In response, the government notified the Flores court that it would begin detaining alien family units together in DHS facilities until a family's immigration proceedings had been completed. The Flores court rejected the government's motion and argument that the preliminary injunction in the Ms. L. lawsuit allowed the government to detain family units together in DHS facilities. In the aftermath of this ruling, DHS appears to have returned to its prior practice of generally releasing family units apprehended at the border that demonstrate a credible fear of persecution pending removal proceedings. However, on September 7, 2018, DHS and the Department of Health and Human Services (HHS), the primary agency responsible for the care and custody of unaccompanied alien minors, published a notice of proposed rulemaking, which, once finalized, w ould allow DHS to detain families together until immigration proceedings were completed. The proposed regulations would create an alternative federal licensing scheme for family residential centers that purports to mimic the standards for the detention of minors set forth in the Flores Settlement, which mandates the use of state-licensed facilities only. This report answers frequently asked legal questions pertaining to the Flores Settlement and the settlement's impact on the detention of alien families apprehended at or near the U.S. border. In particular, the report addresses (1) the background of the Flores litigation, (2) how the Flores Settlement restricts DHS's power to keep families in civil immigration detention, (3) the relationship between the Ms. L. litigation and the Flores Settlement, (4) the executive branch's policy options for detaining or releasing family units apprehended at or near the U.S. border under the Flores Settlement, (5) the September 7, 2018, notice of proposed rulemaking purporting to implement the terms of the Flores Settlement, and (6) the extent to which either the executive branch or Congress can override or modify the terms of the Flores Settlement. Before considering the legal impact of the Flores Settlement on DHS's authority to detain family units arriving at the border without valid entry documents, it is useful to review the relevant statutory framework. The INA contains provisions that govern the detention of aliens in general pending the outcome of removal proceedings. Federal statutes also contain specific provisions concerning the detention of unaccompanied alien children (UACs) who are in removal proceedings. However, neither federal law generally, nor the INA, contains provisions that specifically address the detention of family units or accompanied alien minors for immigration enforcement purposes. Whether they attempt to enter the United States surreptitiously or present themselves at a port of entry, aliens encountered near the border without valid entry documents are generally subject to expedited removal under the INA. Expedited removal is a streamlined process that contemplates removal without a hearing before an immigration judge. Family units, including children arriving with their families, encountered near the border without valid entry documents are subject to expedited removal, but UACs are not subject to this streamlined removal process. If an alien subject to expedited removal "indicates either an intention to apply for asylum . . . or a fear of persecution," then the immigration officer must refer the alien to an asylum officer for a determination of whether the alien has a credible fear of persecution. Aliens who demonstrate such a fear are referred to standard removal proceedings in immigration court for further consideration of their claims for asylum or other relief. The statutory framework that governs the detention of aliens in this situation—that is, where an alien has been referred from expedited to standard removal proceedings after showing a credible fear of persecution—is not straightforward, but its general effect is to permit (without requiring) DHS to detain such aliens pending the outcome of the standard proceedings. First , for aliens referred from expedited to standard removal proceedings following surreptitious entry (i.e., entry or attempted entry into the United States at a place other than a port of entry), the applicable statute is 8 U.S.C. § 1226(a). That statute authorizes DHS to continue detaining the alien, or to release the alien on bond or parole. If DHS decides to keep the alien in detention, the alien is entitled to challenge that decision in a custody redetermination hearing before an immigration judge. Under the standard that governs both the DHS and immigration judge custody determinations, the alien must demonstrate that release on bond or parole "would not pose a danger to property or persons, and that the alien is likely to appear for any future proceeding." Second , for aliens referred from expedited to standard removal proceedings after presenting themselves at a port of entry without valid entry documents, the applicable statute is 8 U.S.C. § 1225(b). That statute provides that such aliens "shall be detained" pending the outcome of the standard removal proceedings in immigration court. But the INA grants DHS authority to release even these aliens on parole. DHS regulations and internal guidance, in turn, instruct DHS officials to make individualized determinations about whether to release such aliens on parole, taking into account factors such as flight risk, danger to the public, and whether the alien has established his identity sufficiently. Recently, in light of evidence that DHS has deviated from this policy in order to detain more aliens for deterrence purposes, two different federal judges in the District of Columbia issued preliminary injunctions ordering DHS to comply with the policy by making individualized parole determinations for aliens detained under § 1225(b). Some federal case law suggests that constitutional principles may limit DHS's ability to detain aliens pending removal proceedings for general deterrence purposes (that is, for the purpose of deterring other aliens from committing civil immigration violations), notwithstanding the statutory authorization in the INA for detention during the removal process. The Supreme Court has yet to resolve this question, however. Federal statutes set forth a separate framework for the treatment of UACs. The Homeland Security Act of 2002 tasks the Office of Refugee Resettlement (ORR), within the Department of Health and Human Services, with "coordinating and implementing the case and placement of unaccompanied alien children who are in Federal custody by reason of their immigration status." Minors remain subject to DHS custody unless and until they are deemed "unaccompanied." Under the Trafficking Victims Protection Reauthorization Act of 2008 (TVPRA), if DHS learns that a person in its custody is an "unaccompanied alien child" (UAC), it must transfer the UAC to ORR custody within 72 hours (unless the child is from a contiguous country, in which case the UAC generally may be given the option to voluntarily return to that country in lieu of being held by ORR and DHS authorities). An alien minor is considered a UAC if (1) the minor has no parent or legal guardian in the United States, or (2) no parent or legal guardian "is available to provide care and physical custody" in the United States. Once a UAC is in ORR custody, ORR must "promptly place[] [the child] in the least restrictive setting that is in the best interest of the child." As noted above, UACs are not subject to expedited removal. The Flores lawsuit began in 1985, reached a settlement in 1997, and remains under the supervision of a U.S. district judge in the Central District of California until the federal government promulgates final regulations implementing the 1997 agreement. Initially, the lawsuit involved a class of unaccompanied alien minors who were apprehended at or near the U.S. border and then detained pending removal proceedings.