When the federal government allowed British Columbia to walk back its experiment with drug decriminalization, the move wasn't surprising to Brittany Maple, executive director of the Matsqui-Abbotsford Impact Society. 

"It's disheartening," Maple said. "We are effectively criminalizing people for existing in public spaces when they have nowhere else safe to exist."

Now, Maple's society has teamed up with a coalition of drug user advocacy groups to take the federal government to court, claiming the…