between two adults. I recall that being raised in one of the previous articles on this issue. It would be not unlike in divorce. Once there is a divorce/settlement agreement in effect, e.g., re child support or custody/visitation, both parties must abide by the terms of the agreement EXCEPT BY MUTUAL AGREEMENT.
So let's say the parents decide that things would be better in reverse: instead of mom having custody (children live with her) and dad has visitation rights, they decide that the children will live with the dad, and mom will have visitation rights. They *have* the right to do that PROVIDED they are in mutual agreement. [I'm not talking about some extenuating circumstance with court-ordered supervised visitation, but just a standard case where parenting capability is not at issue, merely acknowledging that children can't be in two places at once!] The parents can make their own agreement about how it would work; but should there then be some problem, they wouldn't have the right to go to Family Court to have "their" arrangement enforced. BUT, if there *was* no longer mutual agreement, then (from there) terms automatically revert back to the court-sanctioned original.
It's not exactly the same, and a lawyer can weigh in, but it's my understanding that similarly, BY MUTUAL AGREEMENT, with some signed contract waiving certain responsibilities or expectations, you and I agree that I will buy raw milk from you. If everything goes well, that's great. But (not that I'm aware this has ever happened), IF I got sick drinking your milk, I couldn't then go to court and sue you on the grounds that, for instance, there was a law that all milk needed to be pasteurized. Unless you had broken the terms of our contract, I'd have no legal grievance.