One of the great misconceptions of the pre-nuptial agreement is that, as a legally binding contract, once everything has been signed "on the dotted line," this means that the document can no longer be questioned or contested. In fact, nothing could be further from the truth. While a pre-nup is indeed designed to lock down certain things, and a provide some structure and certainty in the event of a divorce, that doesn't mean that it can't be contested.
And one of the things that, in a divorce case, a pre-nup can be easily challenged on is when the conditions in the pre-nup actually violate the law.
You Can't Make Your Own Rules
One of the ways that a pre-nuptial agreement can be completely invalidated, even if it's signed, is when it comes to child support. There are strict laws in place for how child support works, so, in the event of a divorce, if a pre-nup attempts to negate, nullify, or otherwise ignore what the law has already laid out in terms of who is responsible for child support, that pre-nup-or at least that portion of the pre-nup-is unlikely to be recognized or honored in a court of law.
Any conditions of a pre-nuptial agreement that, under ordinary circumstances, would be considered illegal, are not suddenly legal because both people signed to it in a pre-nup. When you are creating a pre-nuptial agreement for the possibility of divorce, it's best not to try to create this document yourself, with what you think are "fair terms." Instead, because this going to be a legal document, get it created and vetted by people with legal expertise, such as divorce lawyers, who can ensure that, should a divorce take place, the pre-nup will provide solid, legally enforceable guidance on what happens next.