The Montreal Police Brotherhood has been ordered by an arbitration tribunal to stop its members from plastering cruisers and city buildings with labour-related stickers.

The stickers, along with police officers clad in camouflage pants and red baseball caps, have been a visual reminder the longstanding conflict between the police union and the city over the province's pension reform law.

Officers have been protesting against the provincial law aimed at overhauling municipal pension plans since shortly after Bill 3 was tabled in June 2014.

Some of the stickers say ''On a rien volé, nous,'' ("We Haven't Stolen Anything'') and "Contre la loi 3'' ("Against Bill 3'').

The controversial law, passed in December 2014, forced municipal workers and retirees to contribute more to their pensions to offset what was at the time a $4-billion pension fund deficit.

The arbitrator, Nathalie Faucher, wrote in her judgment that officers must cease union stickering on "vehicles, signs, buildings ... and service stations and/or the head office of the Service."

The union must also bear the costs for the removal of existing stickers.

The ruling does not apply to stickers on bulletproof vests.

Vandalism vs. freedom of expression

The city argued before the tribunal that the officers' conduct amounted to expensive vandalism against municipal property.

The police brotherhood countered that applying the stickers was a form of freedom of expression and that it did not affect how the officers did their jobs.

In her ruling, released Dec. 29, Faucher concluded there are limits to freedom of expression.

The police brotherhood said Monday there are still stickers out there, but no new ones have been plastered on city property since Faucher's ruling came down.

The union said its lawyers are looking at a possible legal challenge of the decision.

Stickers on fire trucks to remain

The ruling does not apply to Montreal's firefighters, however, a spokesman for their union, Alexandre Dumas, told CBC that its members won't be posting any more stickers.

Indirectly, he said, the arbitration ruling "could have an influence."

Dumas said the union has no plans to remove stickers that are already on the trucks, for now.

Montreal police officers have been wearing camouflage pants and baseball caps as a sign of protest against provincial pension reform since mid-2014. (Graham Hughes/CP)

Camo pants still OK

The arbitration ruling does not address the issue of police officers in camouflage pants and baseball caps, although arguably, the lack of a standard uniform has incensed provincial and municipal politicians more than the sticker campaign.

The former minister of municipal affairs, Pierre Moreau, told CBC in September 2015 that the officers' uniforms are an essential part of their job.

"Sometimes you don't know the difference between a police officer and anybody that is walking on the sidewalk," Moreau said. "If you have to, in an emergency situation, turn back and see whether a police officer is in the vicinity, sometimes it's hard to say, with what they're wearing."

Last July, Public Security Minister Martin Coiteux said his patience with the uniform protest was running out, after a municipal court judge threw out a $1,200 fine for a Laval man. The man had been pulled over by a police officer wearing camouflage pants, and the man claimed he didn't recognize her as a police officer.

Montreal police did ditch their camo pants as a sign of respect for the December 2014 funeral of Jean Béliveau, and again when René Angelil died last year.

However, there was a great outcry when some officers turned up in camouflage pants while working outside the funeral of former premier Jacques Parizeau in June 2015.