[T]he fact of the matter is that the Priestly Society of St. Pius X is in schism since the late Abp. Marcel Lefebvre ordained four bishops without the mandate of the Roman Pontiff. And so it is not legitimate to attend Mass or to receive the sacraments in a church that's under the direction of the Priestly Society of St. Pius X.
https://www.churchmilitant.com/news/article/cdl-burke-sspx-in-schism
