De transactionibus axiomata

LXXX.
Furthermore, a settlement that has been extorted by fear is not valid.

LXXXI.
Therefore, if a plaintiff who has suffered fear initiates a suit using the old action, the defendant, protecting himself with the exception of settlement, will be repelled by a replication of fear. Alternatively, the plaintiff will either seek an action because of fear original: "Quod metus causa" once the old action has been removed by the Aquilian stipulation a formal legal procedure to convert all obligations into a single monetary debt, or he will petition that the release be rescinded and his old action be restored to him.

LXXXII.
However, if a defendant complains about fear brought upon him, he will defeat the action moved by his adversary with the exception of fear.

LXXXIII.
Yet, not just any fear is sufficient to rescind things that have been determined by consent, but it must be such that it would strike a constant man, such as that which contains a danger to life or physical torture.

LXXXIIII.
Furthermore, just as a sentence pronounced by a judge who has been circumvented by false documents is retracted, so too is a settlement—and indeed any pact—entered into on the basis of false documents, once the falsehood is revealed either civilly or criminally, it is rescinded through a restoration to the original state original: "in integrum restitutio".

LXXXV.
So much so, that not even an oath by which a pact or settlement has been confirmed can be an impediment to its being revoked later.

LXXXVI.
This is the case unless, when a question concerning a false document is raised, a settlement has also been made specifically regarding that document, which is what we also asserted above concerning fraud.