MIAMI (AP) – Jose Padilla, a U.S. citizen who was held for more than three years as an “enemy combatant,” pleaded not guilty Thursday to criminal charges alleging he was part of a secret network that supported violent Muslim extremists around the world.

Padilla entered the plea before U.S. Magistrate Judge Barry Garber one week after being transferred from military to civilian custody.

The judge also began hearing arguments to determine whether Padilla should be released on bail, which is opposed by federal prosecutors.

Padilla, 35, was arrested at Chicago’s O’Hare Airport in May 2002 and held at a military brig in South Carolina without criminal charges, initially on suspicion of plotting to detonate a radioactive “dirty bomb” inside the United States.

His case raised questions about whether U.S. citizens detained on American soil could be held without trial in the name of the war on terrorism.

Before the Supreme Court could decide whether to take up Padilla’s case, the Justice Department presented the case to a civilian grand jury, which indicted him in November. The charges do not involve the “dirty bomb” allegations or claims that he plotted as an al-Qaida operative to blow up apartment buildings in major U.S. cities.

Last week, the high court approved Padilla’s transfer to civilian custody in Miami, overruling a lower court that suggested the administration changed tactics and indicted Padilla to avert a Supreme Court ruling on presidential powers during wartime.

Padilla, a former Chicago gang member and Muslim convert, is charged with conspiring to murder U.S. nationals and providing material support to terrorists as part of a North American cell that provided money, material and fighters for violent Islamic jihad. If convicted, he could face a life sentence.

The plea marks Padilla’s first formal answer to any government charge associated with terrorists. His lawyers fought for three years to gain access to the federal courts.

Padilla, who lived for a time in Broward County in the 1990s, is charged in the Florida case along with four others.

They are Adham Amin Hassoun, a Lebanese-born Palestinian who worked as a computer programmer in Broward County; Kifah Wael Jayyousi, Jordanian-born U.S. citizen who worked as a school administrator in Detroit and Washington, D.C.; Mohamed Hesham Youssef, an alleged terror recruit current held in Egypt; and Kassem Daher, a Canadian who is believed to be overseas.