Arizona Christian School Tuition Organization v. Winn, 563 U.S. 125

Arizona provides dollar-for-dollar tax credits (up to $500 individual, $1,000 couple) for contributions to STOs that fund private-school scholarships, including religious schools.
Respondents, Arizona taxpayers, challenge § 43-1089 as violating the Establishment Clause; district court dismissed, court of appeals reversed, and this Court granted certiorari.
Standing in Establishment Clause cases may arise from direct injury, or from a narrow Flast exception for taxpayers, which requires a nexus between taxpayer status and the challenged appropriations under the taxing and spending power.
The majority holds taxpayers lack standing because the STO credit is a tax expenditure, not an appropriation, and Flast’s nexus is not satisfied; the Court reverses the Ninth Circuit and dismisses for lack of jurisdiction.
The decision emphasizes the separations of powers and the necessity of standing in case-or-controversy to prevent broad, non-justiciable rulings.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Does Flast allow taxpayer standing here?	Respondents rely on Flast to establish standing as taxpayers.	The majority rejects Flast applicability to tax credits; no injury traceable to the government	Flast not satisfied; no standing
Is there standing under general Article III requirements?	Respondents are taxpayers with injury in fact from government funding of religion.	Taxpayer status alone is insufficient; injury is speculative and not redressable	No standing under general Article III
Should the method of financing (tax credit vs appropriation) affect standing?	Tax expenditures injure taxpayers similarly to appropriations; standing should extend to tax credits.	Tax credits do not extract and spend the taxpayer’s funds; injury is not direct	Distinction rejects standing; no Flast-based standing
Does injunctive relief against the STO credit redress the claimed injury?	An injunction would stop the alleged constitutional violation by limiting subsidies.	Remedy would not necessarily relief taxpayers; injury is not redressable	Remedy not shown; no standing

Abington Township School District v. Schempp, 374 U.S. 203 (U.S. Supreme Court 1963) (standing for direct injury in Establishment Clause cases mentioned)
Flast v. Cohen, 392 U.S. 83 (U.S. Supreme Court 1968) (narrow exception to taxpayer standing for Establishment Clause challenges)
DaimlerChrysler Corp. v. Cuno, 547 U.S. 332 (U.S. Supreme Court 2006) (tax subsidies and standing; injury theory in spending vs taxation)
Frothingham v. Mellon, 262 U.S. 447 (U.S. Supreme Court 1923) (taxpayer standing general rule; injury must be particular)
Hibbs v. Winn, 542 U.S. 88 (U.S. Supreme Court 2004) (standing discussions in tax-related Establishment Clause cases)