Due process did not prohibit termination of parental rights under Probate Code section 1516.5 where the father waived his rights as a presumed father in a guardianship proceeding. The Court of Appeal held Probate Code section 1516.5 unconstitutional as applied to unwed fathers who have demonstrated a full commitment to parental responsibility under Adoption of Kelsey S. (1992) 1 Cal.4th 816, because due process requires a finding of unfitness. The California Supreme Court reversed, holding that section 1516.5 does not violate due process by adopting the “best interest of the child” standard for terminating parental rights. The statute is open to constitutional challenge as applied to an individual parent. However here, the appellate court erred by deeming the father a Kelsey S. father when he had expressly waived his rights when the child was placed in a guardianship. It is conceivable that a parent faced with termination of his rights under section 1516.5 would be in a position to assert a due process claim based on a showing analogous to Kelsey S., but this is not that case. The undisputed facts here show that the father fell far short of the commitment contemplated in Kelsey S.