The Ecclesia Dei Commission on 18th January 2003, stated that it is possible to satisfy the precept of hearing Sunday Mass by assisting at a Mass celebrated by a priest of the Society of Saint Pius X.
Msgr. Camille Perl of Ecclesia Dei wrote in a letter to Una Voce America in 2003:
"...Points 1 and 3 in our letter of 27 September 2002 to this correspondent are accurately reported. His first question was "Can I fulfill my Sunday obligation by attending a Pius X Mass" and our response was: "1. In the strict sense you may fulfill your Sunday obligation by attending a Mass celebrated by a priest of the Society of St. Pius X." (Source: http://www.cfnews.org/sspx-obl.htm)
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