Motu proprio

A motu proprio (Latin for: "on his own impulse") is a document issued by the Pope (or by a monarch) on his own initiative and personally signed by him.

When issued by the Pope, a motu proprio may be addressed to the whole Church, to part of it, or to some individuals.

The first motu proprio was issued by Pope Innocent VIII in 1484. It continues to be a common form of Papal rescripts, especially when establishing institutions, making minor changes to law or procedure, and when granting favours to persons or institutions.

Effect

An important effect of the issue of a document in this way is that a rescript containing the clause "motu proprio" is valid and produces its effect even in cases where fraud would ordinarily have vitiated the document, since the Pope does not rely on the reasons alleged when he grants a favour. Withholding of the truth in what, according to canonical law, style and practice, must for validity be expressed, normally renders a rescript invalid, but not if the rescript is issued "motu proprio". Consequently, canonists traditionally called the clause the "mother of repose".