Lawyers for Indonesian terror suspect Abu Bakar Bashir say insufficient evidence exists to justify his arrest.
A court hearing has begun of their petition for the release of the cleric.
Police responded that their case against Bashir, accused of being the spiritual leader of the al Qaeda-linked Jemmy Islamic network, was well-documented, and said the cleric had a history of evading justice.
Bashir was arrested on April 30 - as he left prison after serving 18 months on another charge - over suspicions he played a role in the 2002 Bali night-club bombings that killed 202 people, mainly foreign tourists.
Authorities blame the shadowy Jemmy Islamic, seen as a regional offshoot of al Qaeda, for the Bali blasts and other bombings across the world's most populous Muslim nation and elsewhere in Southeast Asia.
Basher's lawyers argued the April arrest had no legal basis.
"There is not enough preliminary evidence to make that arrest. Moreover, police did not show an arrest warrant nor notify the family before taking the action," said Munarman, a member of Bashir's 80-strong legal team.
"The arrest stemmed from intervention and pressure from foreign governments like the United States," Munarman said, arguing that the U.S. Ambassador in Indonesia had tried to persuade Muslim leaders to support the drive to keep Bashir locked up.
Police lawyers said the warrant was given directly to Bashir who refused to take it.
"The criminal violation linked to him has close ties to the bombings in Bali. The accusation was backed by witness testimony and incriminating files," said police lawyer Rudy Heryanto.
"And subjectively, the accused has escaped before to evade the law when he fled to Malaysia."
In 1985 Bashir escaped from a jail term for agitating to set up an Islamic state, slipping away to neighbouring Malaysia. He lived there until 1999, when Indonesian subversion laws used to convict him were repealed.
Police have said they would seek to prove Bashir either gave his blessing for the Bali attacks or was aware of them in his role as the spiritual leader of Jemaah Islamiah.
Bashir's arrest under anti-terrorism laws came just after he finished serving an 18-month jail term for minor immigration offences.
The 65-year-old has denied wrongdoing and insists Jemaah Islamiah does not exist.
He could be held for up to six months for investigation before formal charges are laid and a trial convened.
Previous charges of treason and of leading JI, levelled under the criminal code, were dismissed or overturned.