An "immigration detainer" is a document by which U.S. Immigration and Customs Enforcement (ICE) advises other law enforcement agencies of its interest in individual aliens whom these agencies are detaining. The standard detainer form (Form I-247) allows ICE to indicate that it has taken certain actions that could lead to the alien's removal (e.g., determining that there is reason to believe the alien is removable, initiating removal proceedings). The form also allows ICE to request that the other agency take certain actions that could facilitate such removal (e.g., holding the alien temporarily, notifying ICE prior to releasing the alien). ICE and its predecessor, the Immigration and Naturalization Service (INS), have used detainers as one means of obtaining custody of aliens for purposes of removal proceedings since at least 1950. However, ICE's implementation of the Secure Communities program in the period between 2008 and 2014 raised numerous questions about detainers. This program relied upon information sharing between various levels and agencies of government to identify potentially removable aliens. Detainers were then issued for some of these aliens. The Department of Homeland Security (DHS) emphasized that it prioritized "criminal aliens," those who posed a threat to public safety, and repeat immigration violators for removal through Secure Communities, and the former Director of ICE further instructed that, among "criminal aliens," the focus was to be upon those convicted of "aggravated felonies," as defined in the Immigration and Nationality Act (INA); those convicted of other felonies; and those convicted of three or more misdemeanors. However, there were reports of detainers issued for persons who were not convicted of any offense, or whose sole offense was a misdemeanor. As a result of these and related reports, several jurisdictions adopted policies of declining immigration detainer requests for at least some aliens. Several lawsuits were also filed challenging the detainer practices of state, local, or federal governments. The Obama Administration's announcement on November 20, 2014, that it is replacing the Secure Communities program with a new Priority Enforcement Program (PEP) could effectively resolve certain of these questions and concerns about detainers. PEP is like Secure Communities in that it "will continue to rely on fingerprint-based biometric data submitted during bookings by state and local law enforcement agencies to the Federal Bureau of Investigation for criminal background checks." However, with PEP, detainers are to be issued only for aliens who have been convicted of (rather than just arrested for ) certain offenses that are among ICE's priorities for civil immigration enforcement. Further, with PEP, detainers are generally to be used only to request that state and local law enforcement officials notify ICE prior to the alien's release or transfer to another institution, not to request that state and local officials detain aliens beyond the point when they otherwise would be released for the state or local offense so that ICE may assume custody. Any detainers issued to request detention (as opposed to notification) must generally specify that (1) the alien is subject to a final order of removal, or (2) "there is other sufficient probable cause to find that the person is a removable alien." By way of background, this report surveys the various authorities governing immigration detainers, including the standard detainer form (Form I-247) sent by ICE to other law enforcement agencies. The report also discusses key legal issues raised by immigration detainers, including (1) whether DHS's detainer regulations and practices are within its statutory authority; (2) whether states and localities are required to comply with immigration detainers; (3) who has custody of aliens subject to detainers; and (4) whether detainer practices violate aliens' constitutional rights. In considering these topics, it is important to note that Form I-247 and DHS's detainer practices have changed several times since 2010, including as a result of the actions announced by the Obama Administration on November 20, 2014. Among other actions, the Administration announced the discontinuance of the Secure Communities program, which had arguably prompted many recent questions regarding immigration detainers. ICE and its predecessor, the INS, have long issued detainers for potentially removable aliens, although the case law mentioning such detainers may provide only a partial picture of INS's practices, in particular. For example, in a 1950 decision, a federal district court addressed a challenge to the legality of a deportation order for an alien who was the subject of an immigration detainer requesting his delivery "to the custody of the immigration authorities at the time sentence is fulfilled in the state institute." Later, in a 1975 decision, the Board of Immigration Appeals, the highest administrative body for interpreting and applying immigration laws, heard an alien's challenge to the conditions under which federal prison authorities held him, allegedly as the result of an immigration detainer which requested that the prison notify INS at least 30 days prior to his release. Between them, these two cases illustrate INS's use of detainers to request that a law enforcement agency transfer an alien to INS custody at the completion of the alien's criminal sentence and notify INS prior to the alien's release. However, they do not indicate whether INS used detainers for other purposes, such as to request that a person be held after he or she would otherwise have been released for any criminal offense so that INS could investigate the person's removability and/or take custody. The Immigration and Nationality Act (INA) did not expressly address the issuance of detainers prior to 1986. However, the INS appears to have issued detainers prior to this date pursuant to various powers and responsibilities delegated to it by the INA. Specifically, the INA (1) grants the Attorney General (currently the Secretary of Homeland Security) "the power and duty to control and guard the borders and boundaries of the United States against the illegal entry of aliens;" (2) establishes certain categories of aliens who are barred from admission to the United States, or may be removed from the United States after their admission; and (3) generally grants immigration officials broad discretion as to their enforcement priorities. The INS cited all these provisions, among others, as authority when it ultimately promulgated regulations governing the issuance of detainers, as discussed below, and it seems to have consistently viewed these provisions as broadly authorizing its detainer practices. Neither INS nor ICE appears to have relied upon the "inherent authority" of law enforcement to issue detainers, although at least one jurisdiction has recognized such authority. Then, in 1986, Congress enacted the Anti-Drug Abuse Act, which, among other things, amended Section 287 of the INA to address the issuance of detainers for aliens arrested for "violation[s] of any law relating to controlled substances." Section 287 generally specifies the powers of immigration officers and employees and, as amended, provides that [i]n the case of an alien who is arrested by a Federal, State, or local law enforcement official for a violation of any law relating to controlled substances, if the official (or another official)— (1) has reason to believe that the alien may not have been lawfully admitted to the United States or otherwise is not lawfully present in the United States, (2) expeditiously informs an appropriate officer or employee of the Service authorized and designated by the Attorney General of the arrest and of the facts concerning the status of the alien, and (3) requests the Service to determine promptly whether or not to issue a detainer to detain the alien, the officer or employee of the Service shall promptly determine whether or not to issue such a detainer. If a detainer is issued and the alien is not otherwise detained by Federal, State, or local officials, the Attorney General shall effectively and expeditiously take custody of the alien. After the 1986 amendments, the INS amended its regulations to address the issuance of detainers. The INS initially promulgated two separate regulations, one (codified in 8 C.F.R. §287.7) governing detainers for controlled substance offenses and another (codified in 8 C.F.R. §242.2) governing detainers for other offenses. The final versions of these two regulations were virtually identical, and in 1997, the two regulations were merged into one. This regulation is located at 8 C.F.R. §287.7, the former location of the regulation governing detainers for controlled substance offenses. However, it notes that detainers "are issued pursuant to sections 236 and 287" of the INA. Section 236 authorizes or requires the detention of certain aliens pending their removal, while Section 287 generally specifies the powers of immigration officers and employees (as well as expressly authorizes the issuance of detainers for controlled substance offenses). These detainer regulations currently provide that "[a]ny authorized immigration officer may at any time issue a Form I-247 … to any other Federal, State, or local law enforcement agency," and identify specific personnel authorized to issue detainers (e.g., deportation officers; immigration inspectors). These personnel are the same personnel who are authorized to make warrantless arrests for violations of federal immigration law under certain conditions, as discussed below. In addition, the regulations: require that other agencies requesting the issuance of a detainer provide DHS with "all documentary records and information" related to the alien's status; limit the period for which aliens may be held at DHS's request so that DHS may assume custody to 48 hours (excluding weekends and federal holidays); and specify that DHS is not financially responsible for an alien's detention unless it issues a detainer for, or assumes custody of, the alien. The standard detainer form (Form 1-247) has apparently been in use since at least 1984, and has been amended several times, including in response to criticisms of the Secure Communities program. This form enables ICE to notify another agency that it has (1) determined that an individual is an alien subject to removal based on certain grounds specified on the form (e.g., a prior felony conviction), or otherwise noted by immigration officials; (2) initiated removal proceedings and served a Notice to Appear or other charging document on the alien; (3) served a warrant of arrest for removal proceedings; or (4) obtained an order of deportation or removal for the alien. It also allows ICE to request that the other agency take one or more of the following actions: Maintain custody of the subject for a period NOT TO EXCEED 48 HOURS, excluding Saturdays, Sundays, and holidays, beyond the time when the subject would have otherwise been released from ... custody to allow DHS to take custody of the subject. ... Provide a copy to the subject of th[e] detainer. Notify [DHS] of the time of release at least 30 days prior to release or as far in advance as possible. Notify [DHS] in the event of the inmate's death, hospitalization or transfer to another institution. Consider this request for a detainer operative only upon the subject's conviction. Cancel the detainer previously placed by [DHS] on ____________________(date). The option of requesting that a copy of the detainer be provided to the alien who is the subject of the detainer was added in June 2011, in response to concerns that aliens who were subject to detainers were not always aware of this fact. The option of requesting that the detainer be considered operative only upon the alien's conviction was also added in June 2011, because of criticism that ICE has issued detainers for aliens whose charges were dismissed, or who were found not guilty. ICE also issued guidance and made other changes pertaining to its use of detainers in response to certain criticisms of the Secure Communities program. First, in August 2010, ICE issued an interim policy on detainers that prohibited immigration officers from issuing detainers unless a law enforcement agency "exercised its independent authority to arrest the alien," as well as discouraged officers from "relying" on the hold period purportedly authorized by the detainer form and federal regulations. Then, in December 2011, ICE established a toll-free hotline that detained individuals could call if they believed they were U.S. citizens or victims of a crime. Later, in December 2012, ICE issued guidance that detainers were to be issued only when the subject of the detainer was reasonably believed to be an alien subject to removal from the United States and met certain other criteria. Most recently, on November 24, 2014, when announcing that DHS was discontinuing the Secure Communities program, the Secretary of Homeland Security directed that detainers are generally to be issued only for aliens who have been convicted of (rather than just arrested for ) certain offenses that are among ICE's priorities for civil immigration enforcement. Further, the Secretary directed that detainers are generally to be used only to request that state and local law enforcement officials notify ICE prior to the alien's release or transfer to another institution. They are generally not to be used to request that state and local officials detain aliens beyond the point when they would otherwise be released unless the detainer specifies that (1) the alien is subject to a final order of removal, or (2) "there is other sufficient probable cause to find that the person is a removable alien." The issuance of a detainer for an alien begins a process that could result in the removal of the alien, although ICE does not pick up or attempt to remove all aliens for whom it issues detainers. ICE issued 270,988 detainers in FY2009 and 201,778 detainers in the first eleven months of FY2010 (both years in which the Secure Communities program was operational). It is unclear, however, how many individuals subject to detainers were ultimately removed. It is also unclear how many of these detainers resulted in an alien being held by state or local authorities beyond the time when he or she would otherwise have been released from custody. Numerous questions about detainers were raised in the period between March 2008, when the Secure Communities program began, and November 2014, when the Obama Administration announced it is discontinuing the Secure Communities program and replacing it with a new Priority Enforcement Program (PEP). These questions include (1) whether DHS's detainer regulations and practices are beyond its statutory authority; (2) whether states and localities are required to comply with immigration detainers; (3) who has custody of aliens subject to detainers; and (4) whether detainer practices violate aliens' constitutional rights. This report discusses each of these questions individually below. However, it is important to note that certain questions may have less salience after the discontinuance of Secure Communities than they did while Secure Communities was operational. In particular, certain questions about holds of aliens pursuant to detainers may have been mooted by the Obama Administration's announcement that ICE will generally request such holds only "in special circumstances" when the alien is subject to a final order of removal, or when there is other sufficient probable cause to believe that the alien is removable. Because the INA only addresses detainers for controlled substance offenses, several plaintiffs and commentators have asserted that ICE's detainer regulations and practices exceed its statutory authority and, thus, are unlawful. In particular, those making this argument note that (1) these regulations and practices entail the issuance of detainers for offenses that do not involve controlled substances; and (2) ICE personnel are generally the ones determining whether to issue a detainer. Both things are, they assert, contrary to Section 287 of the INA, which they take to mean that ICE is only to determine whether to issue a detainer for an alien arrested for a controlled substance offense if and when requested to do so by a "Federal, State, or local law enforcement officer" or "another official." Federal immigration authorities, in contrast, have taken a broader view of their authority, issuing detainers for offenses that do not involve controlled substances without a request from a non-immigration officer. In particular, the INS seems to have taken the position that holds are permissible pursuant to its general authority to make warrantless arrests for immigration violations, discussed below, and not Section 287's detainer provisions. The only court to have ruled on this issue to date—the U.S. District Court for the Northern District of California—found that DHS's detainer regulations are within DHS's statutory authority in its 2009 decision in Committee for Immigrant Rights of Sonoma County v. County of Sonoma . In so finding, the court reviewed DHS's regulations in light of the Supreme Court's decision in Chevron, U.S.A. v. Natural Resources Defense Council , which established a two-step test for judicial review of an agency's construction of a statute which it administers: (1) Has Congress directly spoken to the precise question at issue, and (2) If not, is the agency's reasonable interpretation of the statute consistent with the purposes of the statute? Applying Chevron , the court first found that the DHS regulations were not "facially invalid," or contrary to the unambiguously expressed intent of Congress. According to the court: The fact that §[287] does not expressly authorize ICE to issue detainers for violations of laws other than laws relating to controlled substances hardly amounts to the kind of unambiguous expression of congressional intent that would remove the agency's discretion at Chevron step one. Rather, the court finds that because Congress left a statutory gap for the agency to fill, Chevron step two requires the court to defer to the agency's reasonable interpretation of the statute so long as the interpretation is consistent with the purposes of the statute. The court further found that DHS's regulations are "consistent with the purpose of the statute" and "not contrary to the discernible intent of Congress … [g]iven the broad authority vested in the Secretary of Homeland Security to establish such regulations as she deems necessary for carrying out her authority to administer and enforce laws relating to the immigration and naturalization of aliens." Here, the court specifically noted that the detainer provisions in Section 287 of the INA are to be construed "simply [as] placing special requirements on officials issuing detainers for a violation of any law relating to controlled substances, not as expressly limiting the issuance of immigration detainers solely to individuals violating laws relating to controlled substances." The question of whether DHS's detainer regulations and practices are beyond its statutory authority has, however, persisted despite the Committee for Immigrants Rights decision. For example, at least one suit filed against DHS in the early 2010s alleges that the government's "application of the immigration detainer regulations and issuance of detainers … exceeds [its] … statutory authority." It remains to be seen whether and how other courts might address such arguments and what significance, if any, they might attach to the legislative history of the 1986 amendments, which was apparently not considered by the California district court. Although this history is sparse, a statement by the sponsor of the 1986 amendments read on the floor in the House could be construed as indicating that these amendments were intended to expand—rather than restrict—the use of detainers by requiring immigration officers to at least consider issuing detainers when requested to do so by other law enforcement officers. According to this statement, the amendments responded to complaints from state and local officers that INS did not "issue judgment on a suspect's citizenship fast enough to allow the authorities to continue to detain him," and sought to compel INS to take "the necessary actions to detain the suspect and process the case." Questions as to whether states and localities are required to honor immigration detainers seem to have arisen primarily from a DHS regulation which states that: [u]pon a determination by the Department to issue a detainer for an alien not otherwise detained by a criminal justice agency, such agency shall maintain custody of the alien for a period [generally] not to exceed 48 hours ... in order to permit assumption of custody by the Department. This regulation uses the word "shall," and "shall" has been construed as indicating mandatory action when used in other contexts. Thus, the argument has been made that its use here means that states and localities are required to hold aliens whenever DHS issues a detainer calling for them to be held. However, others—including DHS—have taken the position that the regulation's mandatory language applies only to the period of any detention pursuant to an immigration detainer, and does not require detention at DHS's request. Earlier versions of the standard detainer form (Form I-247) may also have contributed to the view that compliance with immigration detainers is required. Indeed, the version of Form I-247 used between 1997 and 2010 expressly stated that federal regulations "required" recipients to hold aliens for up to 48 hours (excluding weekends and federal holidays) so that ICE could assume custody. This form was amended in August 2010 to indicate that ICE "requested"—rather than "required"—that aliens be held. However, DHS further amended Form I-247 in December 2011, in a way that certain affected parties allege created confusion as to whether compliance with detainers is requested or required. Specifically, as amended in December 2011, Form I-247 stated that This request flows from federal regulation 8 C.F.R. §287.7, which provides that a law enforcement agency " shall maintain custody of an alien" once a detainer has been issued by DHS. This language was, however, only used until December 2012, when ICE amended the detainer form yet again to indicate that "detainer request[s] derive[] from federal regulation," without quoting the text of that regulation. Some jurisdictions may also have taken DHS's statements that they were required, at that time, to participate in the Secure Communities program to mean that they must honor detainers issued in conjunction with that program. (DHS announced the discontinuance of the Secure Communities program on November 20, 2014.) The only federal appeals court to have addressed the issue found that states and localities are not required to comply with immigration detainers. Specifically, in its March 4, 2014, decision in Galarza v. Szalczyk , a majority of the reviewing three-judge panel of the U.S. Court of Appeals for the Third Circuit found that the word "shall" in DHS's detainer regulation prescribes the maximum period of any detention, instead of requiring states and localities to hold aliens for DHS. The majority did so, in part, because it construed other language in 8 C.F.R. §287.7 as unambiguously describing detainers as "requests." However, the majority also noted that, if the regulation were seen as ambiguous, DHS's interpretation would "hold persuasive weight," and that DHS and the INS have historically viewed detainers as requests, not commands. The majority also noted other federal court decisions that, while not directly addressing whether states and localities are required to comply with immigration detainers, characterized detainers as requests. The Third Circuit majority also cited the doctrine of constitutional avoidance in support of its interpretation, noting that "[e]ven if there were any doubt about whether immigration detainers are requests and not mandatory orders to local law enforcement officials, settled constitutional law clearly establishes that they must be deemed requests." Specifically, the majority found that the Tenth Amendment's anti-commandeering principle, as articulated by the Supreme Court in New York v. United States and Printz v. United States , means that federal officials cannot require states and localities to detain aliens for them. According to the majority, if states and localities were required to detain aliens for DHS, they would have to "expend funds and resources to effectuate a federal regulatory scheme," something found to be impermissible in New York and Printz . Further, according to the majority, such a requirement would be "exactly the type of command that has historically disrupted our system of federalism" by obscuring which level of government is accountable for particular policies, as was also noted in New York and Printz . The Third Circuit's decision could potentially resolve the uncertainty as to whether compliance with immigration detainers is mandatory, as well as the related debate over whether state and local policies of declining to honor detainers for at least some aliens are preempted by federal law. However, while the Third Circuit's Tenth Amendment concerns, in particular, seem well founded, those who view compliance with immigration detainers as mandatory may continue to assert that compliance with immigration detainers is required based on district court decisions from other jurisdictions , which are not bound by the Third Circuit's decision. For example, at least one district court outside the Third Circuit has expressly rejected the view that the word "shall" in 8 C.F.R. §287.7(d) prescribes the maximum period of any detention, instead of requiring the alien be detained. The term "custody" is generally understood to "encompass[] most restrictions on liberty" resulting from a criminal or other charge or conviction, including arrest or supervised release. Custody is not determined solely by where a person is detained, and the entity by whom the person is physically detained is not necessarily the entity that would be found to have "technical" or legal custody of the person. Who has custody of a detained alien can be significant for purposes of any habeas corpus challenge to the legality of the detention, and potentially also for determining whether any "hold" that may have occurred as a result of the issuance of an immigration detainer was authorized. The writ of habeas corpus has historically "served as a means of reviewing the legality of Executive detention," and detained aliens could challenge the fact, duration, or execution of their detention by federal, state, or local law enforcement. Successfully maintaining a habeas action depends, in part, upon determining who has custody. Federal courts will generally find that they lack jurisdiction if the alien against whom the detainer is lodged is in state custody, while state courts will find that they lack jurisdiction if the alien subject to the detainer is in federal custody. Who has custody could also be relevant in determining whether any "hold" of the alien that results from the issuance of a detainer is authorized. For example, assuming that holds are made pursuant to ICE's general authority to make warrantless arrests—rather than the detainer statute, regulations, or form —questions could arise as to whether state and local officers who are not acting pursuant to a 287(g) agreement have authority to detain an alien found to be in state custody. Such questions could, however, potentially be avoided if the alien were found to be in DHS custody. Whether DHS, or a state or local government, is seen as having custody of an alien for whom a detainer has been issued appears to depend upon how detainers are characterized, as well as the facts and circumstances of the case. Courts in numerous jurisdictions have held that the filing of a detainer, in itself, does not result in an alien being in federal custody. However, these courts have generally viewed detainers as administrative devices, designed to give states and localities notice of ICE's intentions. Thus, their decisions probably cannot be read to mean that an alien for whom a detainer has been issued is never in federal custody. For example, in Mohammed v. Sullivan , the U.S. Court of Appeals for the Eighth Circuit affirmed the district court's dismissal without prejudice of the petitioner's habeas petition because "the filing of an INS detainer with prison officials does not constitute the requisite 'technical custody' for purposes of habeas jurisdiction." The petitioner here was serving a sentence for several drug-related offenses when INS filed a detainer that resulted in a more restrictive security and custody classification being applied. However, the court found that he was not in INS custody for purposes of his challenge to this re-classification. Similarly, in Orozco v. U.S. INS , the U.S. Court of Appeals for the Eleventh Circuit found that the "filing of a detainer, standing alone, did not cause [the petitioner] to come within the custody of the INS" for purposes of a habeas proceeding. The detainer in this case indicated that INS had initiated an investigation to determine whether the petitioner was removable, and the court found that "merely lodging" a detainer with such a notice did not result in INS custody. In certain cases, however, the court has found that an alien is, or at least could potentially be, in federal custody because of the filing of an immigration detainer. For example, in Galaviz-Medina v. Wooten , the U.S. Court of Appeals for the Tenth Circuit found that an alien subject to a deportation order and serving a sentence with the federal Bureau of Prisons was in INS custody as a result of an immigration detainer lodged against him. According to the court, while the lodging of the detainer, in itself, did not result in INS custody, the deportation order "establishe[d] conclusively the INS's right to custody following the expiration of his current term." Thus, because the "INS ha[d] a more concrete interest in this alien," the court found that he was in INS custody. Similarly, in Vargas v. Swan , the U.S. Court of Appeals for the Seventh Circuit rejected the INS's attempt to characterize a detainer as "an internal administrative mechanism" which would not support a finding that the alien was in INS custody. Instead, the court remanded the case for a determination as to whether the jurisdiction receiving the detainer would treat it as a simple notice of INS's interest in a prisoner, or as a request to hold the inmate after his criminal sentence is completed so that INS could take him into custody. Aliens within the United States, including aliens who are unlawfully present, enjoy certain protections under the U.S. Constitution. Among other things, they have been found to be entitled to the protections of the Fourth and Fifth Amendments because they are encompassed by the usage of the word "person " in those amendments. The Fourth Amendment guarantees "[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures," while the Fifth Amendment provides that "[n]o person shall be … deprived of life, liberty, or property, without due process of law." For purposes of the Fourth Amendment, a "seizure" occurs when a person's "freedom to walk away" has been restrained. Similarly, "[f]reedom from imprisonment—from government custody, detention, or other forms of physical restraint—lies at the heart of the liberty" that is protected by the Due Process clause of the Fifth Amendment. In considering whether the detainer practices of federal, state, and/or local governments infringe upon aliens' constitutional rights, courts would probably look at the specific actions taken pursuant to individual detainers, as well as ICE's reasons for issuing the individual detainers, rather than considering detainers in the abstract. Arguments can be made that the mere lodging of a detainer can negatively affect aliens' criminal cases and/or sentences, regardless of the actions that ICE requests of state or local officials. For example, an alien subject to a detainer could be denied bond, or given a more restrictive custody or security designation, because of the detainer. Nonetheless, despite such effects, certain actions pursuant to a detainer would not appear to entail a seizure of the alien's person, or a protected liberty interest (e.g., notifying ICE prior to releasing an alien, or in the event of the alien's transfer or death). Holding a person who otherwise would have been released, in contrast, could be said to result in a seizure of that person and, as such, would implicate protected liberty interests. Such a hold is arguably the equivalent of a new arrest and thus requires independent authority. The authority underlying the initial arrest would not, in itself, permit the hold. However, while holds pursuant to detainers would appear to involve seizures of the alien's person and protected liberty interests, they could still be found to be constitutional, depending upon the grounds for the hold. ICE can use Form I-247 to request holds on various grounds, including (1) a determination that there is reason to believe an individual is an alien subject to removal; (2) the initiation of removal proceedings; (3) a warrant of arrest for removal proceedings; and (4) a removal order. Different grounds could potentially raise different issues. For example, for various reasons explained below, a hold based upon a warrant of arrest for removal proceedings, or a removal order, could be found to raise different issues than a hold based on ICE's determination that there is reason to believe an alien is removable. Arrests pursuant to warrants are presumptively reasonable, and ICE has broad authority to detain aliens for removal. In contrast, authority to hold aliens based on a belief they are removable appears to be more limited. The Fourth Amendment does not prohibit all "seizures" of persons, only those that are "unreasonable." Seizures that are made pursuant to a warrant—including warrants of arrest for removal proceedings—are presumptively reasonable. In contrast, those "conducted outside the judicial process without prior approval by a judge or magistrate, are per se unreasonable…[,] subject only to a few specifically established and well-delineated exceptions." One such exception is where a law enforcement officer has sufficient reason to believe the person arrested has committed a felony. Congress has granted immigration officers similar authority as to immigration offenses. Specifically, Section 287(a) of the INA provides that [a]ny officer or employee of the Service authorized under regulations prescribed by the Attorney General [currently the Secretary of Homeland Security] shall have power without warrant … to arrest any alien in the United States, if he has reason to believe that the alien so arrested is in the United States in violation of any … law or regulation [governing the admission, exclusion, expulsion, or removal of aliens] and is likely to escape before a warrant can be obtained for his arrest, but the alien arrested shall be taken without unnecessary delay for examination before an officer of the Service having authority to examine aliens as to their right to enter or remain in the United States. The listing of officers and employees who are authorized to make warrantless arrests pursuant to Section 287(a) is the same as that of officers and employees who are authorized to issue detainers, and the INS, at least, appears to have taken the position that a detainer placed pursuant to 8 C.F.R. §287.7 "is an arrest" pursuant to Section 287(a) of the INA. Other provisions of immigration law authorizing or requiring the detention of aliens have also been cited as authority for ICE's detainer practices, including Sections 236 and 241 of the INA. Section 236(a) authorizes the arrest and detention of any alien, on a warrant issued by DHS, pending a decision on whether the alien is to be removed, while Section 236(c) requires the detention of aliens who are inadmissible or removable because they have committed certain criminal offenses. Section 241(a)(2), in turn, requires the detention, during the removal period, of aliens found to be inadmissible or deportable on criminal and related grounds, or due to terrorist activities. In addition, at least some commentators would construe Section 287(d) of the INA to authorize the detention of aliens arrested for controlled substance offenses. Whether holds pursuant to an ICE detainer would be found to be authorized by one of these authorities if the alien were found to be in ICE custody has not been definitively settled by the courts. As discussed above, some commentators have asserted that the provisions of the INA addressing the issuance of detainers for controlled substance offenses and the regulations implementing them are the sole authority for holds pursuant to detainers. If this argument were adopted by the courts, then holds pursuant to detainers of aliens who were not arrested for controlled substance offenses could be found to be impermissible. However, even if other authorities were found to be generally applicable, questions could be raised as to whether the holds of particular aliens were authorized pursuant to these authorities. For example, for a warrantless arrest to be permissible pursuant to Section 287(a) of the INA, there must be (1) "reason to believe" that the alien is (a) in the United States in violation of immigration law and (b) likely to escape before a warrant can be obtained for his or her arrest; and (2) the alien must be taken "without unnecessary delay" before an immigration officer having authority to examine aliens as to their right to enter or remain in the United States. "Reason to believe" an alien is in the United States in violation of immigration law has generally been construed to mean that there is probable cause to believe that the alien is in the country in violation of the law. Probable cause, in turn, "exists where the facts and circumstances within [an officer's] knowledge and of which [he] had reasonably trustworthy information [are] sufficient in themselves to warrant a man of reasonable caution in the belief that an offense has been or is being committed." Given this definition, questions could be raised about whether ICE in fact had probable cause to believe that individual aliens were removable based on the information available at the time the detainer was issued (e.g., the alien's immigration status and the offense(s) for which he was arrested or convicted). Moreover, some jurisdictions require an individualized assessment of factors such as ties to the community (e.g., family, home, job) and attempts to flee in determining whether there is reason to believe that an alien is likely to escape before a warrant is obtained for his or her arrest, and a court could find a hold placed without any consideration of these factors is impermissible. Moreover, even when there is reason to believe an alien is unlawfully present and likely to escape before a warrant can be obtained, the arresting officer must generally bring the alien before another immigration officer having authority to examine aliens as to their right to enter or remain in the United States within a "reasonable time" after arrest. ICE regulations provide for some flexibility in determining what constitutes a reasonable time by providing that a determination as to whether to bring formal removal proceedings against the alien will generally be made within 48 hours of arrest, "except in the event of an emergency or other extraordinary circumstance[,] in which case a determination will be made within an additional reasonable period of time." However, in the case of particularly long holds, ICE could be found to have failed to bring individual aliens before an immigration officer within a reasonable time. Additional questions may arise if an alien held pursuant to an immigration detainer is found to be in state custody, not DHS custody. Key among these questions is whether there must be some basis in state law for any action taken by a state or locality pursuant to an immigration detainer, or whether federal law provides the requisite authority for state and local actions. Some jurisdictions have suggested that there must be some basis in state law for any state or local action, and that the federal regulations and forms do not provide the requisite authority. Other jurisdictions, in contrast, appear to have adopted the position that the detainer regulations and/or Form I-247 suffice to authorize state and local actions. However, even in jurisdictions taking the latter view, questions could be raised about whether specific actions taken pursuant to immigration detainers are, in fact, authorized under federal law. For example, in two recent decisions, federal district courts found actual or potential violations of the Fourth Amendment when states or localities held aliens pursuant to immigration detainers so that ICE could investigate the alien's removability. In so finding, both courts characterized such "holds" as "investigatory delays," which are generally seen to run afoul of the Fourth Amendment. Neither court purported to address whether federal law authorizes ICE to hold aliens in order to investigate their removability. However, the courts' findings suggest that these courts, at least, would not view holding an alien in order to investigate his or her removability as authorized by federal law, regardless of whether ICE or the state or locality is "responsible" for the hold. (Section 287 of the INA does not purport to authorize such holds, and DHS no longer includes the option of requesting a hold so that ICE may investigate the alien's removability on its detainer form.) These courts also did not opine on the permissibility of holds pursuant to immigration detainers for purposes other than investigating the alien's removability (e.g., holds when there is probable cause to believe the alien is removable). The Fifth Amendment's guarantee of procedural due process operates to ensure that the government does not arbitrarily interfere with certain key interests (i.e., life, liberty, and property). However, procedural due process rules are not meant to protect persons from the deprivation of these interests, per se. Rather, they are intended to prevent the " mistaken or unjustified deprivation of life, liberty, or property," by ensuring that the government uses fair and just procedures when taking away such interests. The type of procedures necessary to satisfy due process can vary depending upon the circumstances and interests involved. In Mathews v. Eldridge , the Supreme Court announced the prevailing standard for assessing the requirements of due process, finding that [i]dentification of the specific dictates of due process generally requires consideration of three distinct factors: first , the private interest that will be affected by the official action; second , the risk of erroneous deprivation of such interest through the procedures used, and probable value, if any, of additional or substitute procedural safeguards; and finally , the Government's interest, including the function involved and the administrative and fiscal burdens that the additional or substitute procedural requirements would entail. Although the requirements of due process may vary depending on the particular context, the government must provide persons with the ability to contest the basis upon which they are to be deprived of a protected interest. This generally entails notice of the proposed deprivation and a hearing before an impartial tribunal. Additional procedural protections, such as discovery of evidence or an opportunity to confront adverse witnesses, may also be required in certain circumstances to minimize the occurrence of unfair or mistaken deprivations of protected interests. Whether the practices of local and/or federal governments could be found to violate aliens' due process rights under the test established by Mathews would, thus, appear to depend upon the aliens' and the government's interests, as well as existing and potential procedural safeguards. Loss of freedom, such as would result when an alien who would otherwise have been released is held pursuant to a detainer, has historically been seen as carrying significant weight for purposes of due process, although some courts have suggested that the liberty interests of at least certain aliens who entered or remained in the United States in violation of immigration law may be entitled to less weight. On the other hand, the government has been recognized as having some significant interests in the detention of at least certain aliens. For example, in Demore v. Kim , the Supreme Court recognized the government's interest in detaining deportable aliens "during the limited period necessary for their removal proceedings" so as to ensure that they do not flee and, thus, evade removal. Similarly, in Carlson v. Landon , the Court recognized that detention of certain aliens furthers the government's efforts to protect the safety and welfare of the community. Both these interests have been expressly recognized by the courts in upholding, at least in certain circumstances, the constitutionality of provisions of the INA authorizing or requiring the detention of certain aliens pending a decision on their removability or removal proceedings, as previously discussed. Because there are potentially significant interests involved on the part of the alien and the government, the procedural safeguards associated with the issuance of detainers could play a significant role in the court's analysis of any claim that aliens held pursuant to immigration detainers have been deprived of their liberty without due process of law. The nature of these procedural safeguards has evolved over the years, however, as the federal government has amended its detainer form and practices (largely in response to criticism of the recently discontinued Secure Communities program). In particular, Form I-247 was amended in June 2011 to include the option to request that a copy of the detainer be provided to the alien who is the subject of the detainer. Previously, advocates for immigrants' rights had noted that persons subject to detainers were not always aware that detainers had been lodged against them. Even with the June 2011 amendments, however, aliens only have notice of an ICE detainer after it has been issued, not prior to its issuance. In addition, in December 2011, ICE established a toll-free hotline that detained individuals can call if they believe they are U.S. citizens or victims of a crime. This hotline can be seen as responding to criticisms that state and local officials have impinged upon the rights of aliens subject to detainers by using the issuance of a detainer as grounds for holding an alien in excess of 48 hours. The hotline would apparently give certain aliens the opportunity to contest the issuance of a detainer for them. However, there does not appear to be any formal procedure associated with calls to this hotline, and whatever procedure there might be occurs after the issuance of a detainer. Whether these procedural safeguards are adequate to protect against erroneous deprivations of persons' liberty rights remains to be seen. It is also unclear what weight, if any, a court might accord to the fact that persons whom ICE seeks to remove from the United States generally receive a Notice to Appear and have their cases heard before immigration judges prior to their removal. These procedures have generally been seen as providing due process to the individuals involved, although it is unclear whether a court would view the existence of due process in future removal proceedings as sufficient to protect against deprivations of aliens' liberty interests prior to the commencement of such proceedings. Numerous questions about immigration detainers have been raised recently as a result of the Secure Communities program. These questions include (1) whether DHS's detainer regulations and practices are beyond its statutory authority; (2) whether states and localities are required to comply with immigration detainers; (3) who has custody of aliens subject to detainers; and (4) whether detainer practices violate aliens' constitutional rights. The Obama Administration's recent announcement that it is discontinuing the Secure Communities program and replacing it with a new Priority Enforcement Program (PEP) seems likely to lessen the salience of at least some of these questions. Immigration detainers will still be used with the PEP program, but generally only when an alien has been convicted of (rather than just arrested for) certain "priority" offenses. Further, under PEP, detainers will generally be used only to request that state and local law enforcement officials notify ICE prior to the alien's release from custody for the state or local offense, rather than to request that state and local officials hold the alien for a period of up to 48 hours (excluding weekends and holidays) so that ICE may assume custody. Detainers may, however, continue to be used to request holds in cases where (1) the alien is subject to a final order of removal, or (2) there is probable cause to believe the alien is removable. Even this more limited use of detainers could continue to raise questions in particular cases, though. Note also that future administrations could adopt different policies as to the use of immigration detainers, and some Members of Congress have recently introduced legislation that could potentially result in increased use of such detainers. 

Summary: An "immigration detainer" is a document by which U.S. Immigration and Customs Enforcement (ICE) advises other law enforcement agencies of its interest in individual aliens whom these agencies are detaining. ICE and its predecessor, the Immigration and Naturalization Service (INS), have used detainers as one means of obtaining custody of aliens for removal proceedings since at least 1950. ICE's implementation of the Secure Communities program in the period between 2008 and 2014 raised numerous questions about detainers. This program relied upon information sharing between various levels and agencies of government to identify potentially removable aliens. Detainers were then issued for some of these aliens. However, the Obama Administration's announcement on November 20, 2014, that it is replacing the Secure Communities program with a new Priority Enforcement Program (PEP) may moot certain questions, since detainers are to be used differently with PEP than with Secure Communities. Prior to 1986, the Immigration and Nationality Act (INA) did not explicitly address detainers, and the INS appears to have issued detainers pursuant to its "general authority" to guard U.S. borders and boundaries against the illegal entry of aliens, among other things. However, in 1986, Congress amended the INA to address the issuance of detainers for aliens arrested for controlled substance offenses. After the 1986 amendments, INS promulgated two regulations, one addressing the issuance of detainers for controlled substance offenses and the other addressing detainers for other offenses. These regulations were merged in 1997 and currently address various topics, including who may issue detainers and the temporary detention of aliens by other law enforcement agencies. There is also a standard detainer form (Form I-247) that allows ICE to indicate that it has taken actions that could lead to the alien's removal, and request that another agency take actions that could facilitate such removal (e.g., notify ICE before the alien's release). Some commentators and advocates for immigrants' rights have asserted that, because the INA addresses only detainers for controlled substance offenses, ICE's detainer regulations and practices are beyond its statutory authority insofar as detainers are used for other offenses. However, a federal district court in California found otherwise in its 2009 decision in Committee for Immigrant Rights of Sonoma County v. County of Sonoma. Some have also suggested that a federal regulation—which provides that law enforcement agencies receiving immigration detainers "shall maintain custody of the alien for a period [generally] not to exceed 48 hours"—means that states and localities are required to hold aliens for ICE. Prior versions of Form I-247 may also have been construed as requiring compliance with detainers. However, in its recent decision in Galarza v. Szalczyk, the U.S. Court of Appeals for the Third Circuit rejected this view. Instead, it adopted the same interpretation of the regulation that the Department of Homeland Security (DHS) has advanced, construing it as prescribing the maximum period of any detention pursuant to a detainer, rather than mandating detention. In addition, questions have been raised about who has custody of aliens subject to detainers, and whether the detainer practices of state, local, and/or federal governments impinge upon aliens' constitutional rights. Answers to these questions may depend upon the facts and circumstances of particular cases. For example, courts have found that the filing of a detainer, in itself, does not result in an alien being in federal custody, although aliens could be found to be in federal custody if they are subject to final orders of removal. Similarly, holding an alien pursuant to a detainer when there is not probable cause to believe the alien is removable could be distinguished from holding an alien when there is probable cause, or when the alien is subject to a removal order.