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. 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. The Immigration and Nationality Act (INA) did not expressly address the issuance of detainers prior to 1986. 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. After the 1986 amendments, the INS amended its regulations to address the issuance of detainers. §242.2) governing detainers for other offenses. Legal Issues

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. 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. 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 . 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. Courts in numerous jurisdictions have held that the filing of a detainer, in itself, does not result in an alien being in federal custody. 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. 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.
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.