The strongest argument, in my view, would come from the Canadian Charter of Rights and Freedoms and the possibility of an argument that there is an impediment to the right to vote and/or non-discrimination rights. If there were a successful argument along those lines—and I am not aware of any case law that has gone in that direction—it would probably bear not just on indigenous languages, but also on other minority languages in ridings that have populations that are similarly situated in some respects in terms of speaking another language and not having proficiency in English or French at the highest of levels, and thus facing a barrier.
Beyond that, I wouldn't be aware of other legislation.
There would be some who might make an argument around section 35 of the Constitution Act, 1982, but I don't think it can easily apply to a federal election process, as opposed to providing general rights concerning maintenance of indigenous languages.