Comptroller of Treasury of Md. v. Wynne

**Question presented** Does Maryland’s personal‑income‑tax system – which lets residents claim a credit for the “state” income tax they pay to other states but does **not** let them credit the “county” portion of the Maryland tax – run afoul of the Constitution’s “dormant” Commerce Clause (the rule that states may not discriminate against interstate commerce)? **Holding** Yes. The Supreme Court held that Maryland’s tax scheme is unconstitutional because it discriminates against income earned in other states and therefore violates the dormant Commerce Clause. **Core reasoning (in plain language)** *Majority* – Justice Alito, writing for a five‑justice majority (Chief Justice Roberts and Justices Kennedy, Breyer, and Sotomayor joined), explained that a state may not impose a tax that treats the same economic activity differently just because it crosses state lines. Maryland’s rule lets a resident offset only the “state” tax they pay elsewhere, leaving the “county” tax untouched. As a result, income earned out of state is taxed at a higher overall rate than income earned inside Maryland. The Court said this works like a tariff – a classic form of discrimination that the Commerce Clause forbids. The Court also noted that the “internal consistency” test (which asks whether a tax would be fair if every state adopted the same system) shows Maryland’s plan would raise the burden on interstate commerce, so it must be struck down. The fact that the tax is on individuals, not corporations, does not change the analysis. *Dissent* – Three separate dissenting opinions argued that Maryland’s tax does not violate the Constitution. Justice Scalia (joined in part by Justice Thomas) and Justice Thomas (joined in part by Justice Scalia) contended that the credit limitation is a legitimate exercise of the state’s power to raise revenue and does not constitute unlawful discrimination. Justice Ginsburg, joined by Justices Scalia and Kagan, also argued that the scheme is permissible and that the Court’s Commerce‑Clause doctrine should not be applied to invalidate a state’s tax structure. (The dissents did not reach a consensus on the precise reason for upholding the tax, but all maintained that the majority’s view was mistaken.) **Vote breakdown** * Majority (5 justices): Alito (author), Roberts, Kennedy, Breyer, Sotomayor. * Dissenting opinions: * Scalia’s dissent, joined by Thomas for Parts I‑II. * Thomas’s dissent, joined by Scalia except for the first paragraph. * Ginsburg’s dissent, joined by Scalia and Kagan. The Court therefore affirmed the Maryland Court of Appeals and struck down the portion of Maryland’s tax law that denied a credit for the county tax.