A lawyer for the U.S. citizen accused of plotting to attack the United States with a "dirty bomb" told a judge Tuesday her client was being detained illegally.

"My client is a citizen," attorney Donna R. Newman said outside court. "He still has constitutional rights — the right to counsel, the right to be charged by a grand jury. ... And they have not charged him."

After Jose Padilla's arrest in Chicago on May 8, authorities secretly held him in New York City. He was flown Monday aboard a military plane to a Navy brig in Charleston, S.C.

A closed hearing had been scheduled as part of the sealed material witness case. U.S. District Judge Michael Mukasey held the hearing anyway on Tuesday, and opened it to the public.

The judge said Newman's motion to dismiss the material witness warrant might be moot because the government had withdrawn it. But he agreed to review the legal issues raised by the warrant.

Assistant U.S. Attorney Eric Bruce told Mukasey that the government withdrew the warrant and a grand jury subpoena naming Padilla on Sunday before he was turned over to the federal government.

A grand jury was seated in Manhattan shortly after the Sept. 11 terror attacks.

Newman claimed the government has denied her access to Padilla since he was turned over to the Defense Department, apparently on Sunday night. She said he had been held as a material witness in a high-security cell block in Manhattan.

Assistant U.S. Attorney Kenneth Karas declined comment.

Newman said she had filed court papers appealing the decision to place her client in military custody. The papers were not immediately made public.

Newman declined to describe her 31-year-old client other than to say he had been under extremely high security at the Manhattan Correctional Center and that he denied the government's allegations.

"His response is the allegations are not true because there are no allegations. He's not been charged, but he's being detained," Newman said.

Padilla's arrest was revealed Monday by Attorney General John Ashcroft, who described Padilla as an enemy combatant. He said the government has "very significant information" about Padilla's involvement "with Al Qaeda in very serious terrorist plots."

The government described the arrest as a significant blow against an Al Qaeda plot to detonate a radioactive weapon — known as a "dirty bomb" — inside the United States, possibly targeting Washington.

Officials said the plot got only as far as the planning stage and they said there was no indication Padilla had access to nuclear materials. Undersecretary of State John Bollton indicated Padilla was carrying plans for the attack when he was picked up in Chicago.

Authorities described Padilla as a former gang member from Chicago who was raised Catholic but converted to Islam and changed his name to Abdullah al Muhajir.