We believe that our US Constitution applies to all mankind because the rights and liberties that it enshrines are so-called 'natural rights,' or 'inalienable' rights. I think the UN calls them 'universal' rights, but the idea is the same. Human rights don't know national boundaries. That's why I know, for example, that Saudi Arabian state misogyny and violent religious intolerance is wrong, wrong in a "universal" and objective, or cosmic if you please, humanist sense. Our laws and courts don't apply to foreign soil, but the Enlightenment humanist values that authored and echo in our Constitution do.