Someone correct me if I’m wrong, but somewhere I got the idea that only the SSPX bishops are in schism, but not the people who attend their Masses. I don’t know whether or not their priests are considered to be in schism. Most of their sacraments are valid–baptisms, confirmations, holy orders, the Eucharist, extreme unction–but their confessions aren’t. The reason for this is that the priest’s power to absolve sins is not inherent in his ordination–permission is given by the diocesan bishop (this is why one priest cannot hear confessions in another diocese). Since the SSPX is in schism, they don’t have permission from any bishop to hear confessions. Of course, in an emergency situation
any priest can hear confessions and give a valid absolution, even if he’s excommunicated. The SSPX reasons that the current situation in the Church
is an emergency and hence their absolutions are valid. I have no idea if their weddings are valid.
Now, I see no problem with attending a Mass at an SSPX chapel if it is out of love for the Latin Mass (if there is no authorized Traditional Latin Mass) or out of curiosity. It would probably be wise to refrain from receiving the sacraments from the SSPX though (it might actually be sinful to receive from them).
That said, I must say if I was stuck out in the middle of nowhere and the choice was between THIS parish
stjoan.com/
and an SSPX chapel, I’d choose the SSPX hands down!
In that case I would consider it an “emergency situation”!