TORONTO - Ontario's top-ranking police officer is being pressured to attend an Ontario Human Rights Commission mediation session over an arrest made near a Six Nations occupation that some say shows the police treat aboriginal and non-aboriginal protesters differently.

Protester Mark Vandermaas lodged a complaint against OPP Commissioner Julian Fantino and several other police officers after he was arrested in December 2006 while trying to hang a Canadian flag near the occupied site of a former housing development site in the southwestern Ontario town of Caledonia.

Since police did not prevent aboriginal flags from flapping in the wind around the occupied site -- let alone put an end to the occupation altogether -- Vandermaas said his case shows police are enforcing a double-standard.

The complaint is being reviewed by the human rights commission, which has set a mediation meeting for both Vandermaas and Fantino on Oct. 1, and Fantino has 30 days to tell the commission whether he will agree to mediation, documents show.

Neither party is obligated to attend the mediation meeting but will have to be at a "fact finding'' meeting to give evidence as part of the commission's ongoing investigation.

After attempts to get the Caledonia occupation investigated by the provincial police, the community safety minister and the province's ombudsman, Vandermaas said the human rights commission investigation is the first time that allegations of two-tier policing are being examined.

Vandermaas said he wants a written apology from the OPP and a promise that aboriginals and non-aboriginal protesters will be treated the same.

"I would hope that the commissioner (Fantino) sees the writing on wall and realizes that race-based policing is not sustainable,'' he said. "It's not going to be allowed by the citizens of Ontario. I hope he'll come to this meeting in good faith.''

Vandermaas, along with protester Gary McHale, have come under fire for holding numerous rallies against the police handling of the occupation in the beleaguered town -- although neither of them live in Caledonia.

Fantino has made no attempt to hide his contempt, labelling them "mischief makers'' who have cost taxpayers "well over half-a-million dollars'' in increased police resources. Fantino was away Monday and an OPP spokesman couldn't immediately say whether he was planning on attending the mediation meeting.

Jeff Poirier, with the Ontario Human Rights Commission, said privacy considerations prevent him from talking about any complaints lodged with the commission.

The commission is obligated to investigate complaints it receives from the public but parties are always encouraged to resolve their differences through mediation, he said.

"The first thing we always do is offer mediation,'' Poirier said. "We have a good success rate when people agree to attempt mediation . . . But if one of the parties say no, then away it goes to investigation.''