Pollock v. Farmers' Loan & Trust Co.
The 5-4 decision (with one Justice’s vote shifting on rehearing) that effectively voided the 1894 income tax and triggered the constitutional crisis the Sixteenth Amendment resolved. Pollock held that a tax on income from property was, in substance, a tax on the property itself — and therefore a direct tax requiring apportionment under Art. I §§2 and 9.
Pollock has never been formally overruled. The Sixteenth Amendment routed around it for income taxation; the underlying analysis of what counts as a direct tax remains technically alive and would govern any future federal wealth-tax proposal.