They have terms of service. I don't know if I could say it was on those terms of service that they did it, but what they had in their possession was information provided by the RCMP. On top of that, they would also have to do their own assessment because, ultimately, they had to make the determination to cease providing a service to a customer—basically, freezing accounts.
They could also use their own internal programs and search capacity to determine whether there were suspicious transactions that met the definition of the order.