Treaties (including Geneva) are still part of the Supreme Law of the Land

[Bumped w/ Update]

From Article VI:

This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.

In perhaps its most significant decision this term, Hamdan v. Rumsfeld, the Supreme Court held today (.pdf of decision here) that the Guantanamo military tribunals violate the laws of war. Most importantly, as discussed by Marty Lederman at SCOTUSblog and Glenn Greenwald at Unclaimed Territory, the Court held that Common Article 3 of the Geneva Conventions governs as a matter of treaty obligation to all conflicts, including those involving so-called "enemy combatants," the category invented by Administration lawyers to skirt Geneva's rules and allow the President to order prohibited conduct.

The implication is that a wide range of torture and harsh interrogation techniques that arguably do not violate constitutional "due process" obligations remain illegal under Geneva, in which we agreed with the majority of the nations of the world to set higher standards for ourselves--including in conflicts with non-signatory combatants such as Al Qaeda. Additionally, as Greenwald notes: "the Court severely weakened, if not outright precluded, the administration's legal defenses with regard to its violations of FISA," and it "repeatedly emphasized the shared powers which Congress and the Executive possess with regard to war matters."

This is good news for fans of separation of powers and constitutional checks and balances.

Further analysis (via Discourse.net):

Michael Froomkin, Hamden Highlights
Steve Vladeck, After Hamdan: Reclaiming Congressional War Power
Marty Lederman, Legislative Supremacy, The Laws of War, and the Geneva Holding
Jack Balkin, Hamdan as a Democracy-Forcing Decision

Update:

Here's some further reading on Hamden:

Aziz Huq has more at the ACS Blog: Hamdan and the Youngstown Framework

Orin Kerr: Justice Kennedy, Youngstown, and Article II

Mark Graber: Hamdan As What We Make It

Lyle Denniston: Analysis: What Hamdan did not decide

Hilzoy in Hamdan: Clearing Up A Few Points tries to clear up some misconceptions about the decision.