The U.S. Supreme Court, in Elk Grove Unified School District v. Newdow, stated that “in general it is appropriate for the federal courts to leave delicate issues of domestic relations to the state courts.” Consequently, the question at hand has not been dealt with by the Supreme Court or the federal district courts.

The state courts that have handled this issue, for the most part, have not restricted the non-custodial parents from exposing their children to a different religion. The courts will generally steer clear of this issue “except where there is a clear and affirmative showing that the conflicting religious beliefs affect the general welfare of the child” (Munoz v. Munoz, 489 P.2d 1133, 1135 (WA., 1971)).

The ambiguous language from this Washington state case, one of the first to address this issue, has caused other states to interpret what “affects the general welfare of the child” in many different ways. When determining custody, the courts look at and weigh many different factors to determine what is in the child’s best interest. Examples of these factors can include the emotional ties between the parent and the child, the physical and mental health of the parents and/or the ability of the parents to provide for the child's material needs. Religion may be one of the factors considered, but is generally only considered if it has, or will have, a clear and substantial bearing on the welfare of the child. As various courts have stated, a showing of substantial harm must be demonstrated before a non-custodial parent's right to expose the child to his or her religion will be restricted.

State courts have struggled to define what constitutes substantial harm. Very few have found demonstrated substantial harm in the cases they have heard. What courts have said, as in Khalsa v. Khalsa, 107 N.M. 31, 36 (Ct. App. 1988), is that “a custodial parent's general testimony that the child is upset or confused because of the non-custodial parent's religious practice is insufficient to demonstrate harm [See Felton v. Felton, 383 Mass. 232 (1981); Munoz v. Munoz]. Further, general testimony that the child is upset because the parents practice conflicting religious beliefs is likewise insufficient.” Thus a very strong showing of harm must be presented.

An example of this is the case of LeDoux v. LeDoux, 234 Neb. 479 (Neb. 1990) in which the Nebraska Supreme Court upheld a trial court’s decree ordering the father, a Jehovah’s Witness, “to refrain from exposing or permitting any other person to expose his minor children to any religious practices or teachings inconsistent with the Catholic religion.” When they married and had their children, the LeDouxs were both Catholics. At the time of the divorce Edward Ledoux was a Jehovah’s Witness and insisted that the children be involved in his religious activities. The mother, Diane LeDoux, presented testimony from a clinical psychologist who testified that one of the children was under serious stress and was having a maladjustment problem. The psychologist indicated “that conflicts in the Catholic and Jehovah's Witnesses religions were an obvious contributing factor to the stress felt” by the child.

After weighing all the evidence, “the trial court concluded that exposing the minor children to more than one religious practice would have a deleterious effect upon the minor children,” and the Nebraska Supreme Court agreed. (Other examples: Funk v. Ossman, 150 Ariz. 578 (Ct. App. 1986), Kendall v. Kendall, 426 Mass. 238 (1997).)

Because a parent’s constitutional right to practice his or her religion freely could potentially be restricted, a showing of substantial harm to the minor children is required. Substantial harm is a high standard and “requires a clear showing that a parent's religious practices have been or are likely to be harmful to the child” (Kirchner v. Caughey, 326 Md. 567, 576 (Ct. App. 1992)).