One of the first things the Affordable Care Act did was lay new ground rules for how insurance companies operate. Health plans must now allow dependents up to age 26 to enroll on their parents’ insurance, for example, and not charge co-pays for preventive care.

But since states are the primary regulators of health insurance, the federal government can’t act alone. It needed states to pass new laws and change regulations to come into compliance with the law. And that gave states a choice: They could either pass legislation to come into compliance or sit idly by, and invite the federal government to intervene.

Even while many are challenging the health overhaul in the Supreme Court next week, every state except one (Arizona) has decided to do the former, issuing new rules and passing new laws that bring its insurance market in line with Affordable Care Act guidelines, according to a new analysis from the Commonwealth Fund. Some states have moved forward more aggressively than others, coming into compliance with all 10 insurance reforms, while others have taken more limited steps. But nearly every state in the country has done something:

Arizona, for its part, has not formally passed new legislation but has advised its insurers that, if they do not comply with federal regulations, corrective measures will be taken.

“It’s very encouraging that states are moving forward,” concludes Sara Collins, vice president for affordable health insurance at the Commonwealth Fund.

It will be interesting to watch, going forward, whether this is any sort of a preview of how states handle the health insurance exchanges that launch in 2014. Again, states can either set up the marketplace themselves, or cede the task to the federal government. Right now, the landscape is pretty mixed among states that oppose the law. Some are moving forward; some aren’t, often citing the pending Supreme Court challenge. Once that decision comes out - and if it comes out in the Affordable Care Act’s favor - you might see a map on exchanges that looks more like the one above.