The way I have understood verse 65 seems to be how Joseph understood it. "The revelation on marriage required that a wife give her consent before her husband could enter into plural marriage. Nevertheless, toward the end of the revelation, the Lord said that if the first wife “receive not this law”—the command to practice plural marriage—the husband would be “exempt from the law of Sarah,” presumably the requirement that the husband gain the consent of the first wife before marrying additional women. After Emma opposed plural marriage, Joseph was placed in an agonizing dilemma, forced to choose between the will of God and the will of his beloved Emma. He may have thought Emma’s rejection of plural marriage exempted him from the law of Sarah. Her decision to “receive not this law” permitted him to marry additional wives without her consent." https://www.lds.org/topics/plural-marriage-in-kirtland-and-nauvoo?lang=eng