This morning the U.S. Supreme Court ruled that Maryland’s personal income tax regime is unconstitutional. By failing to provide a full credit to its residents for taxes paid to other states, Maryland unconstitutionally created the risk of multiple taxation. The Maryland Court of Appeals was affirmed. The decision was 5-4, with the majority opinion authored by Justice Alito. Dissenting opinions were authored by Justices Scalia, Thomas and Ginsburg.