"Prolonged detention": a Constitutional hurdle

REMARKS BY THE PRESIDENT
ON NATIONAL SECURITY
... Let me repeat: I am not going to release individuals who endanger the American people. Al Qaeda terrorists and their affiliates are at war with the United States, and those that we capture -- like other prisoners of war -- must be prevented from attacking us again. Having said that, we must recognize that these detention policies cannot be unbounded. They can't be based simply on what I or the executive branch decide alone. That's why my administration has begun to reshape the standards that apply to ensure that they are in line with the rule of law. We must have clear, defensible, and lawful standards for those who fall into this category. We must have fair procedures so that we don't make mistakes. We must have a thorough process of periodic review, so that any prolonged detention is carefully evaluated and justified.

A previous post noted that SCOTUS has already decided that Gitmo detainees can avail themselves of habeas corpus (Rasul v. Bush).

The Constitution also provides that "No bill of attainder or ex post facto Law shall be passed."
As explained by Wikipedia:

A bill of attainder (also known as an act or writ of attainder) is an act of the legislature declaring a person or group of persons guilty of some crime and punishing them without benefit of a trial. Bills of attainder are forbidden by Article I, section 9, clause 3 of the United States Constitution.

Me? I'm having a hard time figuring out how Obama proposes to "reshape the standards that apply" to this fifth class of detainess and still comply with the U.S. Constitution.

Hints?