What is the test for a parent's right to separate their children from the other parent?

"Parents and children have a well-elaborated constitutional right to live together without governmental interference." Wallis v. Spencer , 202 F.3d 1126, 1136 (9th Cir. 2000). "That right is an essential liberty interest protected by the Fourteenth Amendment's guarantee that parents and children will not be separated by the state without due process of law except in an emergency."⁹ Id. Moreover, "the interest of parents in the care, custody, and control of their childrenis perhaps the oldest of the fundamental liberty

[980 F.3d 741]