It would be constitutionally-possible to ban a specific religion using s. 33 of the Canadian Charter of Rights and Freedoms (also known as the notwithstanding clause). The legislation would need to explicitly declare that it is to be of full force and effect notwithstanding s. 2(a) of the Charter. The only catch is that such an employment of the notwithstanding clause expires five years after its enactment, unless re-enacted by a resolution of the Honourable the Senate of Canada, and the House of Commons (either House individually can block the renewal, as can the Governor General of Canada).
That would be a flagrant abuse of the NW clause, FP. I think NW Clause should be used only in an emergency, it is a tool in the arsenal of PM to deal with unforeseen situations (or perhaps a rouge Supreme Court).
If some PM were to use it the way you have suggested, I for one would support getting rid of the NW Clause altogether.