SPCA is a non-profit society. I don’t think they have the resources to hunt down puppy mills actively trying to subvert prohibition. RCMP is a national police force. I’m fairly certain puppy mills would fall near the bottom of their priorities list.

This is already a part of the SPCA's mandate, and the RCMP is involved in the shutting down of puppy mills the SPCA discovers under that mandate as well as assisting in abuse cases and the rest of the work the SPCA does that requires a Police presence.