Ex post facto law and the War Crimes Act of 1996?

[Squink]

I ran across several articles on the Administration’s response to the Supreme court’s Hamdan ruling today, and not being a lawyer, found myself confused. Here’s a few representative articles:
Detainee abuse charges feared
Bush administration seeks shield from 1996 War Crimes Act

U.S. seeks to circumvent War Crimes Act

'96 law could lead to war crime charges
Geneva violations were criminalized

troops involved in handling detainee matters might be accused of committing war crimes and prosecuted at some point in U.S. courts.

Senior officials have responded by drafting legislation that would grant U.S. personnel involved in the terrorism fight new protections against prosecution for past violations of the War Crimes Act of 1996. That law criminalizes violations of the Geneva Conventions governing conduct in war and threatens the death penalty if U.S.-held detainees die in custody from abusive treatment.
…
Gonzales told the lawmakers that a shield was needed for actions taken by U.S. personnel under a 2002 presidential order, which the Supreme Court declared illegal, and under Justice Department legal opinions that have been withdrawn under fire, the source said.

Language in the administration’s draft, which Bradbury helped prepare in concert with civilian officials at the Defense Department, seeks to protect U.S. personnel by ruling out detainee lawsuits to enforce Geneva protections and by incorporating language making U.S. enforcement of the War Crimes Act subject to U.S. – not foreign – understandings of what the Conventions require.

To my non-legal mind, the strategy of making a crime legal after the fact, sounds a lot like ex post facto law, which Wikipedia assures me is not permitted under Article I section 9 of the constitution.
So how are they going to get around that detail?

-GQ only please. I’d like to get an answer.

[Billdo]

An Ex Post Facto law is one that criminalizes an action after it occurs.

What is being discussed is decriminalizing actions after they occur, which is Constitutionally acceptable. In fact, the Constitution expressly gives the President the power to pardon, by which he could effectively acheive the same end by granting a blanket pardon.