Certain removable aliens cannot be removed from the United States because they do not have travel documents permitting them to return to their country of origin or because the aliens are more likely than not to be subject to torture if returned to the country of origin.
The U.S. Supreme Court ruled in Zadvydas v. Davis (2001) that such aliens could only be detained following an order of removal for so long as is reasonably necessary to bring about that alien’s removal from the United States, but that the INA “does not permit indefinite detention. http://www.criminalimmigrationlawyer.com/Deportation-Defense.aspx
The Court found that the presumptively reasonable limit for the postremoval-period detention is six months, but indicated that continued detention may be warranted when the policy is limited to specially dangerous individuals, such as terrorists or those in other special circumstances, and strong procedural protections are in place. http://www.simonebertollini1.com/Immigration/Deportation-Defense.aspx
Following the Court’s ruling in Zadvydas, new regulations were issued to comply with the Court’s holding.
ICE generally can only detain an alien beyond the initial 90-day removal period if ICE determines that the alien is likely to abscond if released or that the alien poses a danger to the public, or if ICE is likely to obtain travel documents for the alien in the near future.
Under regulation, ICE may not detain an alien for more than six months unless the alien’s removal is likely in the reasonably foreseeable future, except in special circumstances, including aliens who are detained on account of having a highly contagious disease that is a threat to public safety, serious adverse foreign policy consequences of release, security or terrorism concerns, or being considered specially dangerous due to having committed one or more crimes of violence and having a mental condition making it likely that the alien will commit acts of violence in the future.