The decision on President Barack Obama’s most important domestic policy is in: Requiring people to purchase health insurance is constitutional.

The U.S. Supreme Court ruled Thursday that Congress was correct in requiring nearly every American to purchase health insurance before 2014 or else pay a financial penalty with their tax returns.

The decision in National Federation of Independent Business, et al., v. Sebelius, secretary of Health and Human Services, et al., is an enormous and historic step to repair our health care system and provide coverage to the uninsured. Though it is just that: a step.

Five justices agreed that the fee someone must pay if he or she refuses to purchase health insurance is a kind of tax. Since Congress has taxing power, the individual mandate stands. That’s why it doesn’t matter that the justices didn’t uphold the law on the ground that Congress could use its power in this instance to regulate commerce between states.

The court also held that the part of the Patient Protection and Affordable Care Act that requires states to impose new eligibility requirements for Medicaid, or risk losing funding, is constitutional — as long as states only potentially lose new funding, not all their funding.

The decision was possible because of the swing vote of conservative Chief Justice John Roberts Jr.

According to the U.S. Department of Health and Human Services, so far the law has benefited Mainers by doing the following:

• Allowing parents to keep their children under age 26 on their family coverage. More than 9,000 young Mainers have gained insurance coverage as a result.

• Providing 190,000 Mainers on Medicare with free preventive services, such as mammograms and colonoscopies, in 2011.

• Realigning the spending of health insurance companies, so 80 percent of premium dollars go to providing health care and quality improvements, while 20 percent go to administrative costs. If they don’t, companies must reduce premiums or provide consumers with a rebate. This summer, about 10,600 Mainers are expected to receive rebates.

• Preventing insurance companies from imposing a lifetime dollar limit on health benefits.

• Insuring 41 Mainers in April who were previously uninsured because of a pre-existing condition.

Maine now has to decide how it will run a health insurance exchange, which acts as a marketplace for businesses and consumers to shop for health plans. It may let the federal government run it, partner with the federal government or establish its own. We would like to see the state maintain some control.

Part of setting up the exchange will require the state to determine the requirements for certified insurance plans, which will involve laying out essential health benefits while following established limits on cost-sharing for deductibles, copayments and out-of-pocket maximums.

Maine is one of 26 states that sued to overturn the federal health reform law. But the state will do more good for its people — particularly its poorest — if it accepts the court’s decision. Maine should take advantage of the federal grant dollars available under the act for projects to explore new and streamlined ways to deliver care.

Maine could benefit substantially from the court’s decision, especially when you consider that the state’s health care expenditures represent 19.4 percent of gross domestic product, compared to the nation’s 13.3 percent. A small percentage of the state’s Medicaid population generates a majority of the cost, and providing them with more efficient care will allow the state to cover more people for the same amount of money.

There is still a lot of work to do. The federal government must lay out additional regulations to define how states should implement programs, and Maine must set up its exchange. We’ll wait to see whether the court’s ruling produces a large-enough pool of new customers.

But let’s take a short moment to celebrate. The winners here are the uninsured. About 25 percent of people under the age of 65 in Maine went without health insurance for all or part of 2007-08. The underlying point of the health care law, and any insurance plan, is that risks should be shared between those with more, and those with fewer, risks. And it works best if all people, whether young, old, healthy or sick, participate. The court’s ruling allows for this model to have a chance.