The bottom line: the entire ACA is upheld, with the exception that the federal government's power to terminate states' Medicaid funds is narrowly read.
Tom: Chief Justice Roberts' vote saved the ACA.
The money quote from the section on the mandate: Our precedent demonstrates that Congress had the power to impose the exaction in Section 5000A under the taxing power, and that Section 5000A need not be read to do more than impose a tax. This is sufficient to sustain it.
The court reinforces that individuals can simply refuse to pay the tax and not comply with the mandate.
On the Medicaid issue, a majority of the Court holds that the Medicaid expansion is constitutional but that it w/b unconstitutional for the federal government to withhold Medicaid funds for non-compliance with the expansion provisions.
Justice Ginsburg makes clear that the vote is 5-4 on sustaining the mandate as a form of tax. Her opinion, for herself and Sotomayor, Breyer and Kagan, joins the key section of Roberts opinion on that point. She would go further and uphold the mandate under the Commerce Clause, which Roberts wouldn't. Her opinion on Commerce does not control.