Not that I have heard of. In one of the links here days ago, a group of doctors was discussing removing life support of brain dead patients when the family refused and one doctor told of a story where the family fought it, lied, threatened to keep it from happening. Finally, when all reason with the family had been exhausted, the dr told them the day and time that life support would cease. They refused to show up so the support was removed, the patient died and the next day, the family showed up, expecting that the hospital could not have removed support without their permission.
I believe the law states that the hospital does not need the consent or signature of the next of kin. It is the doctor and the hospital's right and duty to cease life support in such cases. Jahi's mom simply did not understand that the hospital doesn't need her permission. It is out of her hands.