It is not legal for individuals to own or breed rats in Alberta, unfortunately for snake owners!
The regulations are referenced on Alberta Agriculture's web page that states "The Agricultural Pests Act forbids, the importation, sale or captive breeding of Norway rats or any subspecies or derivation of the genus Rattus. Pet shop owners, herpetologists and other persons interested in keeping rats as pets are not allowed to do so in Alberta. Only hospitals, universities and other related institutes of education, authorized by the government are allowed to possess live rattus species of any kind. " Web site for reference is http://www1.agric.gov.ab.ca/
Fortunately there are several good breeders in neighbouring provinces that provide nice feeder rats and usually make it to the herp shows in Alberta - certainly better than pet store prices.