"Further judicial developments pertaining to immigration detainers may be likely, as both the use of and challenges to detainers increase. In particular, future decisions could help clarify whether the issuance of detainers for offenses not involving controlled substances is beyond DHS’s statutory authority. The one federal district court to address the issue found that it is not, but the argument has persisted despite this decision. Future decisions could also clarify whether DHS forms and regulations purport to require state and local compliance with immigration detainers, and whether any attempt to require compliance is prohibited by the Tenth Amendment. Such decisions could also clarify (1) when the federal government could be found to have custody of aliens against whom detainers are lodged; (2) whether and when holds pursuant to detainers are permissible warrantless arrests; and (3) what procedural protections, if any, aliens are entitled to prior to being detained for purposes of an investigation of their removability or on other grounds." - Kate M. Manuel, Legislative Attorney, firstname.lastname@example.org, Congressional Research Service, Aug. 31, 2012.