It’s unfortunate that Chief Justice Roberts joined the liberal justices to uphold the individual mandate as a tax. Yet as I understand the ruling, the opinion does very little to enlarge the federal government’s power and, in key respects, reinforced federalism limitations on federal power. According to SCOTUSBlog, while Chief Justice Roberts concluded the mandate is a tax, he also rejected the Commerce Clause arguments in favor of the mandate. This is significant, because it will limit the ability of Congress to adopt additional mandates in the future. No one will be able to claim such requirements are not a tax, and this will make such requirements more difficult to enact.
Equally important, the majority narrowed the Medicaid provisions substantially in a way that limits Congress’s power to impose conditions on the receipt of federal spending. Specifically, the Court held that Congress may attach conditions on the receipt of new money — in this case the Medicaid expansion — but that Congress may not condition the receipt of funds for separate, pre-existing programs on compliance with the conditions for the new program. In other words, if states refuse to go along with the Medicaid expansion, they don’t lose existing Medicaid funds. If my understanding is accurate, this opinion would mark the firmest limit on use of the spending power in decades, and could constrain lots of future mischief.
UPDATE: Just to underline the point about the spending clause, the vote to narrow the Medicaid expansion was 7–2, as Justices Breyer and Kagan joined the Chief on this.