Why did the Supreme Court find the original Medicaid expansion funding condition unconstitutional?

The Supreme Court found the original Medicaid expansion condition unconstitutional because it was unconstitutionally coercive toward the states.12

Under the Affordable Care Act, the federal government threatened to withhold all federal Medicaid funding—including support for existing beneficiaries—from states that chose not to participate in the new expansion. Because Medicaid funding represents an enormous portion of state budgets, the Court determined that this threat functioned as a "gun to the head," effectively removing any legitimate choice for states to opt out of the program.1

Chief Justice John Roberts, writing for the majority, emphasized that while Congress may attach conditions to federal spending, those conditions cannot cross the line from pressure into compulsion. By forcing states to implement a federal program under the threat of losing essential existing funds, the government undermined the political accountability necessary for a federal system, as state officials would be forced to bear the consequences of a program they had no real power to reject. To remedy this, the Court ruled that the Secretary of Health and Human Services could not withhold existing Medicaid funds from states that declined the expansion.312