Is the constitution untouchable?

The latest Supreme Court ruling effectively quashed Prime Minister Stephen Harper's efforts at Senate reform. Canada's highest court says in order to change the red chamber, the constitution is clear: the government would need the approval of seven of the 10 provinces, with half the country's population. Political observers say that even with public support and political will, it would take a Herculean effort at federal-provincial relations to hit that mark. But what does it say about the constitution, and a government's ability to adapt it? We asked retired parliamentarians Val Meredith, Lorne Nystrom, and Martha Hall Findlay to weigh in.