Under the Immigration and Nationality Act § 240(b)(5), an immigration judge must order an immigrant removed in absentia if the government proves the immigrant received proper notice of the hearing and still failed to appear, unless exceptional circumstances apply. Once issued, an in absentia order makes an immigrant immediately subject to deportation. The order can be reopened only on narrow grounds: lack of proper notice, exceptional circumstances such as a serious illness, or the immigrant was in federal or state custody. The Supreme Court has further limited the ability to reopen these orders. In absentia orders have become a primary throughput mechanism in the immigration enforcement system — they allow courts to "close" cases without adjudicating them on the merits.