In a 2-1 decision by the U.S. Court of Appeals for the D.C. Circuit, the court ruled that that Guantanamo Bay detainees cannot use the U.S. court system to challenge their indefinite imprisonment. The ruling dismisses hundreds of cases filed by foreign-born detainees in federal court and also threatens to strip away court access to millions of lawful permanent residents currently in the United States, upholding a key provision of the Military Commissions Act of 2006. The law set up a Defense Department system to prosecute terrorism suspects, and detainees must prove to three-officer military panels that they don't pose a terror threat (several Senate Democrats are co-sponsoring legislation which restores habeus corpus rights for detainees, but Bush would veto as long as he's in office).
Now, an appeal to the Supreme Court is almost certain, and it's likely the Court will agree to take the case. Twice before, the Supreme Court has ruled that the right of habeus corpus found in the U.S. Constitution gives Guantanamo detainees access to courts. Of course, changing this was the intended purpose of the Military Commissions Act, since Congress is Constitutionally empowered to set the jurisdiction for federal courts, including appellate jurisdiction for the Supreme Court.
However, for all intents and purposes, the Supreme Court interprets its own jurisdiction and it's possible enough Justices will conclude that such a fundamental right of the Constitution is at stake and Congress can't prohibit all review. Associate Justice Anthony Kennedy, seen by many as the sole "swing voter" on the Court, mostly agreed with the liberal side in past Guantanamo rulings. If he does so here, there would be a majority to strike down this provision of the Military Commissions Act as unconstitutional.