"It was an illegal detention, they were not arrested lawfully," said Daan Mostert.
They were arrested on a farm in Balmoral, Mpumalanga, on Thursday on charges of being in possession of illegal weapons.
Ratte, a soldier with the Rhodesian army and the apartheid-era South African Defence Force, has already served four years in jail after being found guilty of sabotage in 2001 - in relation to a 1997 break-in at the Pomfret military base in the Northern Cape.
Mostert said their urgent application would be heard in the North Gauteng High Court in Pretoria at 14:00.
'Internal Boer refugees'
Meanwhile, the group appeared in the Witbank Magistrate's Court on Monday morning, and the case was postponed to October 11 for a bail hearing, said police spokesperson Captain Leonard Hlathi.
Mostert had unsuccessfully tried to make the application for their release on Saturday. They also allegedly had a number of different uniforms in their possession, he said.
Hlathi did not have their names immediately available, but Beeld newspaper reported on Saturday they were: Eugene Becker, 48, Justin Schoeman, 18, Günther Kotze, 32, Corné de Beer, 22, Petrus Visser, 20, Marais Bouwer, 30, Raymond Senekal, 43, Wesley Borman, 24, and Christopher Meyer, 27.
A web site www.afrikaner-genocide-archives.blogspot.com described the people arrested with Ratte as impoverished "internal Boer refugees" who were on the farm to learn the building trade.
It was claimed that the police arrived without search or arrest warrants, and that suggestions of terrorism in media reports were part of a propaganda campaign by the media and police, akin to homosexuality claims against slain Afrikaner Weerstandsbeweging leader Eugene Terre'Blanche.
The website says that due to South Africa's black economic empowerment laws, more than 800 000 "Boers" reportedly live in 460 internal-refugee camps countrywide.
Another website, Censor Bugbear, claimed the farm housed a "Boer Genocide" museum with disabled Boer-era weaponry.