The conviction against Osama bin Laden's former driver, Salim Hamdan, was thrown out by a US federal court on Tuesday, on the grounds that material support for terrorism did not constitute a war crime during the time period he was prosecuted for.

Agence France Presse said Hamdan had already served his sentence and been freed, but the decision could impact the cases of other detainees at Guantanamo who were also charged with providing "material support for terrorism."

The federal appeals court reversed Hamdan's conviction saying that a military commission improperly applied a law that wasn't retroactive, ABC News reported. Hamdan was convicted under the Military Commission Act of 2006, but the three-judge panel said today that his conduct from 1996 to 2001 did not fall under the federal statute in effect at the time.

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"At the time, the international law of war did not proscribe material support for terrorism as a war crime,” Circuit Judge Brett Kavanaugh wrote today, according to Bloomberg. “Hamdan was not charged with aiding and abetting terrorism or some other similar war crime."

Kavanaugh also said, "But the issue here is whether 'material support for terrorism' is an international-law war crime. The answer is no," according to AFP.

"International law leaves it to individual nations to proscribe material support for terrorism under their domestic laws if they so choose. There is no international-law proscription of material support for terrorism," he added.

Raha Wala, a lawyer for Human Rights First, told Reuters that the decision undermines the legitimacy of the military commission system, along with calling into question the prosecution of offenses that are not recognized as war crimes internationally. "All of these prosecutions are now in jeopardy," he said, of the pending cases.

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