More than 1,000 arrests were made during the summit last weekend amid allegations peaceful demonstrators, or even bystanders, were caught up in mass arrests, The Toronto Star reported Thursday.
The Canadian Civil Liberties Association says it has been overwhelmed with phone calls and complaints.
"The CCLA is planning to help people who are seeking compensation to (initiate) a lawsuit in the Superior Court of Ontario," said Nathalie Des Rosiers, CCLA general counsel. "We have a couple of plaintiffs."
Police Chief Bill Blair said police officers' actions were justified because violent protesters infiltrated peaceful demonstrations or protesters failed to disperse when asked.
Blair has announced an internal police review but there are growing demands for a public inquiry, the Star reported.