“Part of Roberts’ decision, joined by the dissenters, limited the federal government’s ability to dictate how states use Medicaid funds—and in a way that could have serious effects. Roberts and the conservatives accepted the argument that the federal government effectively coerced the states by threatening to withdraw existing Medicaid funds if they do not expand the program, as the Affordable Care Act calls upon them to do.
This makes the expansion of Medicaid essentially voluntary. The federal government is picking up most of these costs, so most states will take the deal anyway. But states could decline to expand if they chose—and it’s not clear (to me) what happens then. In addition, that part of the ruling could limit the federal government’s leverage over states in the future.”
-Jon Cohn, “Supreme Court Rules, Obamacare Can Go Forward”