What canon law would that be? And how would that apply in a state of necessity?
I don't receive Holy Communion, nor do I go to confession at the local SSPX chapel, because they don't allow it, since I'm not registered there. Not a big deal. They have a right to regulate their sacraments. Evidently, you don't agree with that.
No, they have no right to refuse the Sacraments to any Catholic who is in good standing and not in a state of public sin. I'm not sure where you're getting it that they refuse Communion and Confession to people who are not registered. I've never known that to be an SSPX policy. If you saw something about it in the bulletin, it's undoubtedly a reference to the other Sacraments, like Baptism, Confirmation, Holy Matrimony. I've gone to many SSPX chapels where I'm not a registered member and have received the Sacraments without issues. So if I belong to an SSPX chapel in Cleveland but then am out of town in, say, Chicago, I can't go to Communion there because I'm not registered with the chapel. It sounds like you're misinterpreting something here.
People have cited the Canon Law where the faithful have a right to receive the Sacraments. I don't have it off hand. Even the SSPV has re-stated this, that the only reason the Sacraments can be refused to a Catholic in good standing is due to public sin, except they classify lots of things as public sin. Sacraments are not given to the SSPX to control at their whim, and I know of no priest of the SSPX who believes that either. Just a before Vatican II, a Catholic can got to any Catholic Mass anywhere and receive the Sacraments without prior registration.
Your statement referring to "THEIR" Sacraments could not be more mistaken. These are NOT "THEIR" Sacraments.