I think Canada would need to look at its own national security interests. I have to say that I'm not sufficiently familiar with your own national security concerns to know whether you should join, but I would say that looking alliance-wide, it's very important that we take seriously the unintended consequences of the development of such technologies.
Missile defence will be essential if the world is to seriously move towards reduced and then zero nuclear weapons, but if we do so simply with our own security in mind and do not take into account the unintended consequences in terms of the reactions from states like Russia, China, and those in the Middle East, then we're only storing up trouble for the future.