The $45-million proposed class action lawsuit was spearheaded by Sherry Good, a 51-year-old office administrator who says she was corralled by cops for four hours when police in riot gear used a tactic called kettling.
But today a judge ruled that it can't proceed as a class action, saying its "broad, sweeping nature" is problematic.
A statement from lawyer Murray Klippenstein's office says they will appeal the decision.
More than 1,000 people were detained by police that weekend in June 2010 after protesters using so-called Black Bloc tactics broke away from a peaceful rally and ran through the downtown, smashing windows and burning police cruisers.
The vast majority of those detained were released without charge within 24 hours.