Political activist Badrul Hisham Shaharin was arrested today ahead of the "Save Malaysia" rally planned for Malaysia Day this weekend.
Badrul, popularly known as Chegubard, was detained outside the PAS headquarters in Kuala Lumpur, where he was believed to be attending a meeting.
He was taken to the Dang Wangi police headquarters in Kuala Lumpur.
The demonstration was organised by Perikatan Nasional to protest the attorney-general's controversial decision to halt the corruption trial of Deputy Prime Minister Ahmad Zahid Hamidi.
Zahid, the Umno president and Barisan Nasional chairman, had faced 12 counts of criminal breach of trust, eight of corruption, and 27 of money laundering involving tens of millions of ringgit belonging to Yayasan Akalbudi.
He was given a discharge not amounting to an acquittal or DNAA on Sept 4 after deputy public prosecutor Mohd Dusuki Mokhtar informed the judge of the request by the Attorney-General's Chambers to discontinue all proceedings against him.
According to the organisers, the demonstration will be held at Kampung Baru and is expected to be joined by NGOs and civil society groups.
Deputy police chief Ayob Khan Mydin Pitchay had warned of action against the rally organisers, saying they must comply with requirements under the Peaceful Assembly Act (PAA).
He said that according to Section 9(1) of the PAA, any party intending to hold a rally must apply for a permit five days in advance.
Electoral watchdog Bersih, however, one of many who had urged the authorities to allow the gathering in line with the right to peaceful assembly, said Ayob's statement was "factually incorrect".
"This is factually incorrect, as the Peaceful Assembly Act 2012 only requires rally organisers to notify the authorities, not apply for permits or approval like in the old days," it said.
Rights group Lawyers for Liberty had also hit out at the government over its response, reminding it against invoking the PAA, a law used by previous Barisan Nasional governments against protesters that critics say is unconstitutional.