The union insists the city council in Trois-Rivieres, Que., ignored the presumption of innocence when it expanded the municipal officers' suspension to take away their pay.
Union president Louis Lesage says the officers' families are in disarray after being deprived of their income.
The officers were suspended with pay on Feb. 8, but city council revised the suspension to one without pay in a decision at their Monday night council meeting.
Lesage says the union will attempt to help the officers financially and challenge the suspensions if city council doesn't reverse its decision.
Police officers Marc-Andre St-Amant, Barbara Provencher, Dominic Pronovost and Kaven Deslauriers face seven charges, including assault with a weapon, assault causing bodily harm, negligent use of a firearm, fabricating police reports and obstruction of justice.
There are also charges against the original suspect, Alexis Vadeboncoeur, who is accused of armed robbery at a pharmacy.
A surveillance video shows four people beating a man in a parking lot on Feb. 2. The incident attracted international attention once the video hit the Internet.
The video shows a young man dropping a weapon and laying on the ground, face down. Police officers arrive running, and level a flurry of punches and kicks.
Police say in their report that the man resisted arrest.
Vadeboncoeur alleges that he was struck in the head and the genitals.