The Supreme Court handed the Obama administration a key victory, upholding the tax credits that allow many low-income Americans to purchase health care insurance in states where the federal government is running the insurance marketplace. These tax credits, available to Americans with household incomes between 100% and 400% of the federal poverty line, operate as a form of premium assistance that subsidizes the purchase of health insurance.

The petitioners in King v. Burwell, No. 14-114 (U.S. June 25, 2015), challenged a ruling from the Internal Revenue Service (IRS) and claimed that a phrase in the Affordable Care Act (ACA) indicating that the subsidies are only available to consumers buying insurance in a state-run exchange prohibited the federal government from providing tax credits where states have not established their own exchanges. Arguing that the text of the law should be read literally, they challenged an IRS regulation that makes these tax credits available regardless of whether the exchange is run by a state or the federal government.

But the Supreme Court sided with the Obama administration in its 6-3 decision, emphasizing that language allowing tax credits for health insurance purchased on “an Exchange established by the State” must be interpreted in context and within the larger statutory scheme. Chief Justice Roberts, who authored the majority opinion, wrote that the phrase “an Exchange established by the State” was ambiguous, and therefore required the Court to look to the broader structure of the law. He wrote that the larger statutory scheme required the Court to reject the petitioners’ interpretation, which would have destabilized the individual insurance market and would create the exact same “death spirals” of rising premiums and declining availability of insurance that the law was crafted to avoid. In passing the law, he added, Congress sought “to improve health insurance markets, not to destroy them.”

The Supreme Court’s analysis went a step beyond the traditional framework used by courts to review agency actions. This two-step analysis, first announced in Chevron U.S.A. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984) and widely known as the Chevron two-step, first considers whether the statutory language is clear—and if it is, the inquiry ends there. But if the language of the law is silent or ambiguous, a court next considers whether the agency’s interpretation of the statute is reasonable, granting considerable deference to the agency’s interpretation. Because the tax credits under the ACA are central to the reforms created by the law, Chief Justice Roberts explained, Congress would not have delegated such an important question to any agency, and especially not to the IRS, which lacks expertise in crafting health insurance policy. He wrote that in this case, the task of determining the correct reading of the statute belonged to the Court.

For most providers and companies involved in the health care system, the result of this decision means business as usual. But the decisive victory for the law today means that the ACA is here to stay, and will have a permanent effect on how patients access care. Insurers and providers still must overcome hurdles to achieve affordable premiums and provide improved care for patients across the country. And as more laws are sorted out in the courts, the Supreme Court’s reliance on context in interpreting the statute today could set an important precedent of emphasizing the purpose of major legislation when analyzing its trickier provisions.