Though Medicare was from the outset an entitlement under federal law, the status of Medicaid has always been less certain. Arguably, it was the Supreme Court, rather than Congress that first recognized that Medicaid recipients (and providers) could sue the states in federal court to enforce federal Medicaid requirements. A recent widely reported federal court decision, however, called radically into question the continuing existence of a federal Medicaid entitlement. Though this decision has now been reversed, and rejected by other courts, it illustrates the tenuous nature of the Medicaid entitlement, and the need to reconstitute Medicaid as an exclusively federal program.
Timothy Stoltzfus Jost, The Tenuous Nature of the Medicaid Entitlement, Health Affairs, 22, no. 1 (2003): 145-153.