A class action suit has been filed against the city of Montreal and its police force following a night that saw more than 518 people arrested.

UQAM student Jean-Pierre Lord is spearheading the lawsuit, contending that he and more than 500 other people were unlawfully arrested and fined on the night of May 23, 2012.

That night, following more than three months of daily protests. police declared a protest illegal at 8:30 p.m. and began kettling protesters at midnight.

Hundreds were detained for several hours and released after being fined $634 each.

In his filing, Lord contends that the police reports about the protest that he read on Twitter convinced him the protest was legal, and so he decided to join it at 10 p.m.

He argues that when he tried to leave the protest several hours later he was not allowed to leave, and was one of those placed under arrest.

At the time police said that the crowd was ordered to disperse around 12:30 a.m when members of the crowd pelted officers with projectiles.

He is seeking $2,500 in damages, and wants all the other people arrested that night to receive the same award.

The day after the mass arrests Montreal police commander Ian Lafreniere said 518 people were arrested, including some innocent bystanders, and apologized for police detaining people with kettling tactics.