Congress will help pay for your roads, but your state can’t lower its drinking age below 21. There’s federal money for colleges, but they can’t discriminate against women in the classroom or on the athletic field.

Federal cash comes with strings. Now 26 states are telling the Supreme Court that President Barack Obama’s health care law has stretched an old rule too far. The new law’s requirements for expanding Medicaid amount, in their view, to coercion that violates the U.S. Constitution’s division of power between the national government and the states.

No lower court has sided with the state plaintiffs. But the justices have reserved time next Wednesday to hear the Medicaid issue as part of their broad review of challenges to the health care overhaul. And their decision could have implications far beyond health — for federal aid for housing, law enforcement, education and transportation.