EXCLUSIVE: Former Attorney General Bill Barr is supporting a new amicus brief at the Supreme Court, led by Democratic attorney David Boies, opposing Maine's decision to block public tuition from flowing to students who choose to attend religious schools.

The Supreme Court agreed this summer to take up the case, Carson v. Makin, which stems from a Maine program that provides tuition for Maine residents to attend private high schools if their local district does not have a public school.

"Maine’s law is the reflection of the relentless campaign of secularization intent on driving every vestige of traditional religion from the public square," said Barr in a release from the Defense of Freedom Institute for Policy Studies (DFI).

"Maine has no objection with providing funds to students to attend private schools that aggressively instruct children about behaviors that reflect the progressive values and practices of contemporary America. Yet, in alarming contrast, Maine’s law targets and excludes those schools that instruct students on the religious practices commanded by their faith, forcing families to choose between abandoning their religious convictions and foregoing needed public assistance to which they are otherwise entitled by law. This is an unacceptable violation of the First Amendment and religious discrimination of the worst kind."

SUPREME COURT TO HEAR CASE ON MAINE TUITION PROGRAM THAT BARS MONEY FOR RELIGIOUS EDUCATION

The state says it can't discriminate against schools based on their status of being connected to religious institutions. But it says it can ban money from going to the school if it promotes a certain religious view to its students – something many religious schools do. 

It comes in the wake of a recent Supreme Court case that ruled the government can't ban government aid in a generally available program from going to religious schools. 

The previous case, Espinoza v. Montana, was considered a major win for religious liberty advocates. But the Maine program includes different language that, if upheld, could effectively neuter Espinoza.

Friday's brief was filed by David Boies, a Democratic attorney who represented former presidential candidate Al Gore in Bush v. Gore. One of the attorneys at Boies' firm reportedly helped former Democratic presidential nominee Hillary Clinton with debate prep. 

CLICK HERE TO GET THE FOX NEWS APP

"The Free Exercise Clause of the First Amendment prohibits the Government from imposing religious-based restrictions on the personal decisions of individual citizens," said Boies. "Here, the State attempts to use religious criteria to decree to which secondary school parents may send their children simply because the parents receive generally available tuition assistance. This law strikes at the heart of, and is clearly prohibited by, the Free Exercise Clause."

The First Circuit Court of Appeals, which upheld Maine's law, said that because the Maine program applies only to students who do not have access to public schools, those who seek religiously "intertwined" education are not seeking "equal access" to the benefit of a free education. 

Former Secretary of Education Betsy DeVos said, "Sadly, religious discrimination has been tolerated for too long, not only through prohibitions on religious schools like the Maine law but also through other needless restrictions on students like bigoted Blaine Amendments."

Fox News' Tyler Olson contributed to this report.