I would say it's both section 7 and section 15. The Carter claim itself was about section 15 and section 7, and Justice Smith started with section 15, and 7 was a bit of an afterthought. The Supreme Court of Canada said yes to section 7 therefore we don't need to deal with 15.
So the challenge on behalf of the vulnerable could be, again, both, but I think in that context the section 15 equality claims would be the more powerful ones.