Under the Laken Riley Act “federal detention” means DHS (through U.S. Immigration and Customs Enforcement’s Enforcement and Removal Operations) must take custody of eligible noncitizens and hold them in federal immigration custody rather than releasing them to the community. The statute amends 8 U.S.C. §1226(c) to require the Secretary of Homeland Security to issue a detainer and “effectively and expeditiously take custody” of an alien charged with or convicted of specified offenses; detention generally continues through immigration proceedings and the removal period as authorized by the INA (i.e., until removal, a bond decision, or other law-based release).