Pope John Paul II declares that Archbishop Lefebvre and other SSPX leaders are automatically excommunicated, because of the consecration of 4 bishops against the pope's express wishes. Furthermore, those who formally adhere to this schism are also excommunicated.
Draws on the criteria of several reputable cult experts. Does the SSPX have the characteristics of a manipulative, spiritually unhealthy religious cult? This site says yes.
Detailed, sometimes repetitious, examination of canon law. Concludes that Lefebvre was never truly excommunicated but that since his death the SSPX has drifted into schism.