In Flast v. Cohen, the Supreme Court addressed whether taxpayers have standing to challenge federal spending as violating the Establishment Clause of the First Amendment. The case arose when a group of taxpayers sued over federal funds being used to purchase textbooks for religious schools, arguing that it violated separation between church and state. In an 8-1 decision, the court held that taxpayers do have standing in cases where a constitutional violation could be tied directly to specific congressional appropriations rather than general tax revenue disbursements. This ruling expanded taxpayer standing beyond what had been established by Frothingham v. Mellon (1923), which generally barred taxpayer suits on grounds they were too remote from potential injury caused by government action.

In the dissenting opinion for Flast v. Cohen, Justice Harlan argued that taxpayers should not have standing to challenge federal spending on religious schools under the Establishment Clause of the First Amendment. He contended that there was no logical connection between taxpayer status and the type of legislative enactment attacked; thus, he believed it inappropriate to grant standing based solely on this status. Furthermore, he expressed concern about opening up a floodgate of litigation by individuals who disagreed with government policies but suffered no direct harm or interference with their rights from those policies. In his view, such disputes were better resolved through political processes rather than judicial intervention.