Meadwestvaco Corp., Successor in Interest to Mead Corp. v. Illinois Department of Revenue

Summary

The Supreme Court vacated the Illinois Appellate Court's decision, holding that state courts erred in using an "operational function" test to justify apportionment without first determining if the taxpayer and the sold asset formed a unitary business. The Court clarified that prior precedents did not create a new ground for apportionment absent a unitary relationship. Justice Thomas concurred, expressing doubt about the constitutional basis for such limitations but joining the opinion as it applies existing precedents.