The Supreme Court started its new term on Monday with arguments in a difficult and consequential case over California's attempt to cut Medicaid payment rates. The justices were not focused on the ultimate question of whether state officials were entitled to address the budget crisis there by lowering payments to medical providers. Rather, they considered the threshold question of whether the providers and Medicaid recipients were entitled to sue over the move. The answer was obscured by a tangle of legal doctrines and practical concerns. Medicaid is a joint federal-state program that provides health care to poor and disabled people. States are not obligated to participate. If they do, they receive federal money and in exchange agree to pay rates "sufficient to enlist enough providers" to ensure that care available under Medicaid is similar to that available to other local residents. There is no question that federal authorities can enforce the law and that states that fail to comply with their obligations face the loss of federal money. Almost as soon as the argument was under way, though, Justice Ruth Bader Ginsburg said such enforcement standing alone was problematic.