The Supreme Court case Committee for Public Education and Religious Liberty et al. v. Regan, Comptroller of New York, et al., 1979 revolved around the issue of state funding to religious schools in New York State. The plaintiffs argued that such funding violated the Establishment Clause of the First Amendment which prohibits government from making any law "respecting an establishment of religion". However, the court ruled in favor of Regan with a 5-4 decision stating that as long as state aid was used for secular purposes like testing services or record keeping and not directly supporting religious activities, it did not violate constitutional principles separating church and state. This ruling upheld a previous decision made by Lemon v Kurtzman (1971), where criteria were established to determine if laws intended to give aid to parochial schools breached these principles.

In the dissenting opinion for the case Committee for Public Education and Religious Liberty et al. v. Regan, Comptroller of New York, et al., Justice William J. Brennan Jr., joined by Justices Thurgood Marshall and John Paul Stevens, argued that providing state aid to religious schools violated the Establishment Clause of the First Amendment. They believed that such funding could lead to government entanglement with religion as it would require extensive auditing to ensure funds were not used for religious purposes - a task they deemed impossible given how intertwined secular and religious activities are in parochial schools. The justices also expressed concern about potential political divisiveness along religious lines due to public financing of private religions through taxes; this was seen as an inherent risk when government becomes involved in financial support for religion or its exercise.