The U.S. Supreme Court should appreciate the real issue at stake in the Espinoza voucher case, the Freedom From Religion Foundation urges as oral arguments start Wednesday in the lawsuit.

FFRF’s 18-page friend-of-the-court brief, filed in November jointly with Center for Inquiry, American Atheists and the American Humanist Association, cogently argued that true religious liberty would be endangered if the court strikes down a provision of Montana’s Constitution that prohibits funding religious education.

“Religious liberty is imperiled in this case,” its brief asserted. “But this case is not about discrimination; it is about government-compelled support of religion. Every Montana citizen has the right to not be taxed to fund religion.”

When the Montana Legislature adopted a neo-voucher scheme, the Montana Supreme Court held that the scheme violated the “No Aid” clause of the state Constitution and struck down the entire neo-voucher scheme, for all private education, religious and nonreligious. Christian parents, represented by the pro-voucher Institute of Justice, want the U.S. Supreme Court to declare that No Aid clauses violate the Free Exercise Clause of the U.S. Constitution. Nearly 90 percent of Montana’s private schools are affiliated with religion. If the Court declares No Aid clauses unconstitutional, FFRF warns, all taxpayers may be compelled to fund religious worship and religious education. The 26 percent of nonreligious Americans will be the hardest hit.

An ironic additional consequence of such a ruling might be to bring down regulation on churches and religious schools due to the flow of public money into religious schools. In short, a judgment in favor of the plaintiffs would fundamentally alter the state-church relationship in place since the nation’s founding.

This is the first time the Supreme Court has taken up the constitutionality of state constitutional provisions against funding religion since its 2017 ruling in Trinity Lutheran Church v. Comer. The justices ruled 7-2 that Missouri’s constitutional ban on funding religion and churches was in violation of the free exercise clause of the First Amendment, holding that a church had to be able to compete with secular groups for grants. FFRF strongly urges the U.S. Supreme Court to rule this time to maintain the constitutional wall of separation between state and church.

The brief points out the Supreme Court’s historic understanding of the First Amendment means that government cannot subsidize religion: “No tax in any amount, large or small, can be levied to support any religious activities or institutions,” as the Supreme Court has significantly ruled. The brief takes up the mantle of defending the rights of all citizens, asserting that “the court ought not to strike down No Aid provisions when they have served this country so well in protecting religious liberty.”

The Freedom From Religion Foundation, based in Madison, Wis., a 501(c)(3) nonprofit educational charity, is the nation’s largest association of freethinkers (atheists, agnostics), and has been working since 1978 to keep religion and government separate.