On the Friday before Christmas, U.S. Immigration and Customs Enforcement (ICE) released new guidance on immigration “detainers, online ” the lynchpin of agency enforcement programs involving cooperation with local police. In the new guidance, ICE Director John Morton instructed agency employees to only file detainers against immigrants who represent agency “priorities.” Unfortunately, as with prior agency memos on prosecutorial discretion, the detainer guidance is so riddled with loopholes that it could have little—if any—practical effect. The new guidance defines “priorities” so broadly as to make the term virtually meaningless. As is now well known, immigration detainers are requests (not commands) sent by ICE to local jails asking for selected inmates to be held even after they would otherwise be entitled to release. Although the federal government has issued detainers for decades, their use has become especially common following the expansion of Se Communities…