Carson v. Makin revolved around the limitations of school vouchers in Maine, which prohibited the use of these vouchers for religious-based private schools. In a 6–3 decision, the Supreme Court ruled that Maine's restrictions violated the Free Exercise Clause, as they discriminated against religiously affiliated schools. Dissenting justices argued that this decision undermined the long-standing principle of separation of church and state, as it would require state governments to fund religious institutions.

Many states in the U.S. provide tuition assistance for private schools through school vouchers, but some have incorporated Blaine Amendments into their constitutions, which prohibit funding for religious schools. Justice Breyer, joined fully by Justice Kagan and partially by Justice Sotomayor, expressed concerns in his dissent that the ruling could compel states to use taxpayer money to fund religious schools. He noted that the decision largely ignored the First Amendment's establishment clause while focusing heavily on its free exercise clause, breaking with historical precedent that had never mandated state funding for religious education within tuition programs.

In her separate dissent, Justice Sotomayor pointed out that the Court had shifted from allowing states to decline funding for religious organizations to requiring them to subsidize religious indoctrination with taxpayer dollars. She argued that the ruling continued to erode the wall of separation between church and state that the framers of the Constitution sought to establish.