This article focuses primarily on California law (which essentially parallels the views of the majority of other states). U.S. Constitution principals are discussed as well.

General Rule:

“A parent will not be enjoined (prohibited, legally prevented) from involving a child with the parent's religious activities absent a clear affirmative showing of harm.” In re Marriage of Weiss (1996) 42 Cal.App.4th 106.  

The Weiss case involved a written prenuptial agreement that stated that the child would be raised Jewish.  Upon the divorce, the wife returned to her Christian roots and involved the child in Sunday school, a Wednesday Christian club and Christian camp.  The appellate Court found that the husband did not establish a clear and affirmative showing of harm, and ruled that the agreement related to religious was, therefore, constitutionally unenforceable.  The Court stated that the wife has an “inalienable [i.e., no human has the authority to deny or take away] First Amendment right to the free exercise of religion, which includes the right to change her religious beliefs and to share those beliefs with her offspring.”

Weiss cited heavily from a well-researched and well-reasoned case, namely, Zummo v Zummo (PA App 1990) 574 A2d 1130, where, before being married, a couple, despite their religious differences, orally agreed to raise their children in the Jewish faith.  After 10 years of marriage, the couple separated, and the husband desired to take the children to Roman Catholic services while he had custody of them. The wife objected to this alleging that such would disrupt the children’s formal Jewish training and would confuse them. The appellate court held that the oral prenuptial agreement impermissibly entangled the court in religious matters and unconstitutionally limited the parents in religious matters in the absence of persuasive evidence showing substantial harm.  

 The court in Zummo stated that "the speculative possibility of mere disquietude, disorientation, or confusion arising from exposure to 'contradictory' religions would be a patently insufficient 'emotional harm' to justify encroachment by the government upon constitutional parental and religious rights of parents, even in the context of divorce."  “[P]arents [are] be free to doubt, question, and change their beliefs, and that they be free to instruct their children in accordance with those beliefs" “unless the …beliefs or conduct of the parent are demonstrated [by competent evidence] to present a substantial threat of present or future, physical or emotional harm to the child.” If harm is established, any restriction must be “the least intrusive means adequate to prevent the specified harm."

U.S. Constitution:

The United States Supreme Court specifically has held parental authority in matters of religious upbringing may be encroached upon only upon a showing of a "substantial threat" of harm to the "physical or mental health of the child or to the public safety, peace, order, or welfare." (Wisconsin v. Yoder (1972) 406 U.S. 205, 230.  Yoder explained "only those interests of the highest order and those not otherwise served can overbalance legitimate claims to the free exercise of religion." (406 U.S. at p. 215).

 In Yoder, the US Supreme Court held that, per the First and Fourteenth amendments, the state may not compel or force Amish parents to send their children to formal high school up to age sixteen.

Other California Cases:

The case of In re Marriage of Murga (1980) 103 Cal. App. 3d 498, involved a noncustodial parent's right to express religious beliefs. The court upheld the majority view in other states that refuse to restrain the noncustodial parent from exposing the minor child to his or her religious beliefs and practices, absent a clear, affirmative showing that these religious activities will be harmful to the child."

Murga also observed that "[t]he refusal to intervene in the absence of a showing of harm to the child reflects the protected nature of religious activities and expressions of belief, as well as the proscription against preferring one religion over another." Additionally, Murga took into consideration the California public policy to assure minor children of "frequent and continuing contact with both parents after the parents have separated or dissolved their marriage.”

"[H]arm to the child from conflicting religious instructions or practices...should not be simply assumed or surmised; it must be demonstrated in detail." In re Marriage of Mentry (1983) 142 Cal. App. 3d 260. In re Marriage of Mentry, the appellate court invalidated a restraining order which prohibited the father from engaging the children in any religious activity, discussion, or attendance during visitations and from providing them with articles, publications, or other religious materials.

Harm to Child:

Courts will intervene in parental choices about religious training when it is necessary to prevent harm to the child. Prince v Massachusetts (1944) 321 US 158 (Jehovah's Witness mother could be prosecuted under the child labor laws for using her children to dispense literature in the streets despite her religious motivation for doing so.  The court found no constitutional infirmity in "excluding [these children] from doing there what no other children may do.");  Jehovah's Witnesses v King County Hospital (WD Wash 1967) 278 F.Supp.488, affirmed (1968) 390 US 598 (Court permitted blood transfusion to child over parents' religious objection).