The man accused of plotting to attack the United States with a radioactive "dirty bomb" is being held illegally, his lawyer told a judge.

"My client is a citizen," Donna R. Newman said outside court Tuesday. "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.

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.

U.S. District Judge Michael Mukasey said Newman's motion to dismiss the material witness case against Padilla might be moot because the government withdrew it. But he agreed to review the legal issues raised by the warrant.

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

Padilla's mother, Estela Ortega, had testified before the grand jury two weeks ago but did not expect her son to be detained, said her lawyer, Victor Olds.

Ortega "never heard anything from him or any place else for one moment to suggest that he was involved or ever was involved with a terrorist organization," Olds said.

Maria Rossello, Padilla's maternal grandmother, said her grandson had been in "Arabia" for the past five years but the family did not know what he was doing there.

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.

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

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.