because of their solemn, public form. Among types of papal legislation, apostolic letters issued motu proprio are next in solemnity. Examples include the "Constitution on the Liturgy" (Sacrosanctum Concilium) and the "Constitution on the Catechism of the Catholic Church." Another example is Pope Pius XII's Munificentissimus Deus, the dogma of the Blessed Virgin Mary's Assumption.

By their nature,