A Toronto judge has blasted police tactics during last year's G20 summit.

Lawyers defending some of the people charged with offences in connection with last year's summit say a Toronto judge's ruling this week is going to have "an enormous impact" on their cases.

The case in question involved Michael Puddy, who took part in a demonstration on Saturday June 26, at the corner of Spadina Avenue and Queen Street West.

Puddy was on his way to a concert when he decided to join the peaceful protest.

Minutes later he had been pushed to the ground and cuffed with plastic restraints. He was held in custody for two days.

Police testified Puddy had a 15-centimetre knife attached to his belt.

Puddy, 32, from London, Ont., was eventually charged with obstructing police, concealing a weapon and possession of a prohibited weapon.

The first two charges were dismissed three months ago. On Thursday Puddy was found not guilty on the third charge.

His lawyer, Adam Goodman, said Puddy had "no intention to obstruct the police or cause any trouble," yet he was arrested.

The arrest of a man during last year's G20 summit in Toronto was 'completely unjustified,' a judge says. (Kimberley Gale/CBC)

Justice Melvyn Green accepted Puddy's defence that he was not carrying the knife as a weapon and further ruled that since the arrest was illegal, so too was the search that uncovered the knife.

Puddy's arrest, he wrote, was "completely unjustified."

Green's judgment caused a stir because of its harsh criticism of police tactics. He said police officers acted as the aggressors that evening.

"The only organized or collective physical aggression at that location that evening was perpetrated by police each time they advanced on demonstrators," Green wrote.

He went on to say that the "zealous exercise of police arrest powers in the context of political demonstrations risks distorting the necessary if delicate balance between law enforcement concerns for public safety and order, on the one hand, and individual rights and freedoms, on the other."

Defence lawyer Howard Morton, who has two clients still facing G20 charges, said he thinks the ruling is "going to have an enormous impact."

"For the first time we have the outrageous conduct of the police that weekend being examined in a judicial setting in a criminal trial," said Morton.

"The judge called it what it was, outrageous police conduct."

Lawyers say the Ontario Court of Justice ruling will not set a precedent, but it will help to bolster defence arguments in future cases.