Canonum De Ius Positivum
Canons of Positive Law
IV. Consensus
4.5 Consensus Dispute and Extinction
Article 140 - Alteration
Canon 2386 (link)
The Form of a Consensus Instrument can never be altered without the express written permission of all the parties.
Canon 2387 (link)
The alteration of a Form of a Consensus Instrument without consent constitutes fraud.
Canon 2388 (link)
The terms of a Consensus Instrument can never be altered without the expression written permission of all the parties.