A decision from the Supreme Court of Canada has already thrown out at least one child luring conviction and could jeopardize others.

Douglas Morrison's case started with a posting on Craigslist that read "Daddy looking for his little girl," court documents show, and a police officer "posing as a 14-year-old girl named Mia" who responded.

An Ontario judge eventually convicted Morrison, an Ontario man, of child luring.

Court records show that the two had sexual conversations online, but never met.

Morrison's lawyers argued that he had been "role playing" and didn't believe "Mia" was actually underage.

But at the time, the law was written in such a way that the accused had to provide evidence to prove he did not believe she was underage. Otherwise, it would be assumed he did.

Now, the Supreme Court has unanimously ruled that law violates the charter of rights because it shifts the burden of proof onto the accused to prove they're innocent.

Criminal defence lawyer Rishi Gill defended Mountie Dario Devic, who had a child luring charge stayed and eventually pleaded guilty to breach of trust.

"What they did was go too far and the courts pushed them back," Gill told CTV News. "Do I think it's going to shift monumentally how the Crown has to deal with these cases? Absolutely."

In their decision, SCC justices wrote that "prosecutorial convenience and expediency cannot justify the risk of convicting the innocent," adding that "the Crown must prove beyond a reasonable doubt that the accused believed the other person was underage."

The decision raises questions about whether Creep Catchers stings or cases like the Vancouver police operation which snared 47 suspects over the past year will hold up in a court of a law.

"It's a little bit too early to tell, but we are aware of it and we're looking at the actual ruling," Vancouver police Sgt. Jason Robillard.

Crown lawyers say they're studying the ruling to see if and how it will impact current cases, but can't speculate right now on what that impact might actually be.

Meanwhile, the decision means that Morrison will get a new trial.

With files from CTV Vancouver's David Molko