The Supreme Court's dormant (commerce) division

Today the Supreme Court issued its decision in Comptroller of the Treasury v. Wynne, a constitutional challenge to the structure of Maryland's income tax. The Court held, 5-4, that Maryland's income tax is unconstitutional insofar as state residents do not receive credit for taxes paid on income earned out-of-state. Such taxation, the Court held, violates the Dormant Commerce Clause because it discriminates against interstate commerce. The decision is interesting for several reasons.

[Supreme Court: Maryland has been illegally double-taxing residents who pay income tax to other states]

Although the Court split 5-4, it did not divide along traditional ideological lines. Justice Alito wrote for the Court, joined by the Chief Justice and Justices Kennedy, Breyer and Sotomayor. Justices Scalia, Thomas, Kagan and Ginsburg dissented, with all but Kagan writing an opinion. Justice Ginsburg argued the Court's result was not dictated by existing precedent while Justices Scalia and Thomas reiterated their complaints about existing dormant commerce doctrine (or "negative Commerce Clause" doctrine, as they like to call it). In their view, the Court's dormant commerce clause jurisprudence is lacks sufficient grounding in the Constitution's text.

Some commentators (myself included) have claimed the current Court is prepared to relax dormant commerce clause scrutiny, but there's little evidence such a shift is coming in Wynne. It may still happen, though. Keep an eye on the various dormant commerce challenges to state-level energy and climate policies (e.g. subsidies for in-state renewable power, low-carbon fuel standards, etc.). These cases could split the Court is interesting ways as multiple justices would be presented with a stark conflict between their views of the dormant commerce clause and their views about environmental regulation.

UPDATE: For more on the Court's divisions in these cases, check out these posts from Michael Greve (Law & Liberty) and Michael Ramsey (Originalism Law Blog).