The battle waging in Indiana to de-fund Planned Parenthood may become the first significant legal challenge to flow from NFIB v. Sebelius, and Chief Justice John Roberts’ rewriting of the rules governing the conditions the federal government can and cannot attach to federally-subsidized state spending may have given conservative state lawmakers just the opening they had hoped for.

In May, lawmakers in Indiana passed a bill that prevents Medicaid from contracting with any entity that provides abortions. The bill essentially stripped millions of dollars in funding from Planned Parenthood in knowing violation of the Medicaid rules and placed the state among others in a conservative crusade to kill off the women’s health care provider.

According to those rules, states largely get to design their own programs for providing health insurance coverage for low-income people, but they cannot ban providers from participating in the program solely on the basis of the range of medical services they provide — especially family planning services. Federal law already prohibits the use of any federal funds, including Medicaid funding, from providing for abortions, so this would seem to be a settled issue. Furthermore, US Senator Richard Blumenthal (D-CT) and twenty-nine other Senate Democrats issued a letter to Health and Human Services (HHS) Secretary Kathleen Sebelius requesting that HHS officials advise Medicaid directors not to implement measures to prevent Medicaid or Title X funding from going to clinics that offer abortion services, making it clear that Democrats had the administration’s back in a fight over funding. HHS rejected the Indiana law.

Prior to NFIB v. Sebelius, the idea of an outright challenge to the federal strings attached to Medicaid spending seemed preposterous, just like prior to NFIB v. Sebelius the idea that Congress didn’t have the ability to tax and spend to regulate the health insurance industry wasn’t treated with any seriousness by a majority of legal scholars.

Oh what a difference one opinion can make.

Thanks to the majority in NFIB v. Sebelius, conservative states looking to enact state-wide funding bans may have the framing necessary to pin the federal government. That’s because the language of Roberts’ opinion as to the Medicaid expansion is vague enough to argue that the federal government can’t coerce a state into funding Planned Parenthood by threatening to withhold all of that state’s federal Medicaid money, especially, since conservative states argue, they believe cutting Medicaid funds is the only way to guarantee state dollars do not fund abortion services.

Now, to be clear, Roberts takes great pains in his opinion on the Medicaid expansion to ground the outcome in the particular facts of the expansion under the ACA and the two-fold carrot-and-stick approach to getting states to expand their Medicaid coverage for low income Americans. But, much like the Supreme Court’s decision upholding the federal partial birth abortion ban in Carhart v. Gonzalez, such precision can actually create more room for legal challenges than less. Roberts’ opinion doesn’t delineate the contours of when the federal government is and is not being unconstitutionally coercive to the states in a conditional grant situation.

That means the lower courts will get to parse those boundaries out while fighting over how far, or if at all, they can challenge federal rules that prohibit them from discriminating against the health care provider. And it’s a good reminder that while the immediate victory in the Affordable Care Act was certainly something to celebrate, as the details of the decision play out women’s health advocates could find themselves stuck with some very bad law.