The RCMP for many years in many of its reports has been saying that the principal source of income for most criminal groups in Canada is the drug trade. What they don't say—what they omit to say—is the very obvious: the reason the drug trade is so lucrative is because of drug prohibition, meaning the application of the criminal law to drugs creates a fantastically lucrative black market.
That is why the drug trade in Canada, if you believe the RCMP, is the principal source of financing for criminal organizations. It's also one of the principal sources of funding for terrorist and insurgent groups around the world.