I can only answer for what it'd be here in Oklahoma. Which means in many states, even maybe Oklahoma
, the following will be wrong:
Postnuptial agreements are unenforceable unless they are in contemplation of divorce,
i.e., an impending divorce. If she agreed to this amount within the context of settlement negotiations of the marital estate, then the deal is enforceable as a contract and can be defended with the sorts of affirmative defenses which would apply in contract law,
e.g., fraud, duress, mistake,
etc.
What the husband would do (at least in Oklahoma courts, at least I if was working on his case) is file a Motion to Enforce Settlement Agreement. At that point, if you can prove that you had a deal,
i.e., a signed settlement agreement, then you've got a decently solid case and here he could force her to accept a Decree of Dissolution of Marriage which specified the $43 million.
On the other hand, if this is just something they did as a matter of estate planning or something to that effect, it'll likely be held to have no effect. At any rate, again, the article is pretty weak on the crucial details, at least from a legal perspective.
This is not legal advice, do not read this and rely on it. If you are trying to skip out of a settlement for a $43 million portion of a marital estate, I recommend you contact a lawyer post haste.