MIAMI -- President George W. Bush does not have power to detain American citizen Jose Padilla, the former gang member seized on U.S. soil, as an enemy combatant, a federal appeals court ruled Thursday.

Padilla (pictured), who used to attend the Dar Uloom Mosque in Pembroke Pines is accused of plotting to set off a "dirty bomb" that uses conventional explosives to spread radioactive material. He was picked up amid much fanfare in May of 2002 and has been in a Navy brig in Charleston, S.C., ever since.

The court's decision could force the government to try Padilla in civilian courts.

In a 2-1 ruling, a three-judge panel of the 2nd U.S. Circuit Court of Appeals said Padilla's detention was not authorized by Congress and that Bush could not designate him as an enemy combatant without the authorization.

The court directed Defense Secretary Donald Rumsfeld to release Padilla from military custody within 30 days, but said the government was free to transfer him to civilian authorities who can bring criminal charges.

If appropriate, Padilla can also be held as a material witness in connection with grand jury proceedings, the court said.

"As this court sits only a short distance from where the World Trade Center stood, we are as keenly aware as anyone of the threat al-Qaida poses to our country and of the responsibilities the president and law enforcement officials bear for protecting the nation," the court said.

"But presidential authority does not exist in a vacuum, and this case involves not whether those responsibilities should be aggressively pursued, but whether the president is obligated, in the circumstances presented here, to share them with Congress," it added.

The government said Padilla proposed the dirty bomb plot to Abu Zubaydah, then al-Qaida's top terrorism coordinator.

Only two other people have been designated enemy combatants since the 2001 terrorist attacks: Ali Saleh Kahlah Al-Marri, a citizen of Qatar who has been accused of being an al-Qaida sleeper agent, and Esam Hamdi, a Louisiana native captured during the fighting in Afghanistan.

In its ruling, the court said it was not addressing the detention of any U.S. citizens seized within a zone of combat in Afghanistan.