The way the building code works is that at a national level it's a model code. If it's adopted at the provincial level then it's enforceable. The large majority of the provinces and territories have adopted the codes related to radon. Several of them are now taking them and making them more stringent as they have more data available with regard to the risk of radon in their provinces and municipalities.
On June 18th, 2015. See this statement in context.