The Supreme Court may have upheld the Affordable Care Act’s individual mandate, but it struck down part of President Obama’s Medicaid expansion. The latter move has gotten less attention but could create some big political changes, including paving the way for states to lower their drinking ages.

Seeking to make more people eligible for Medicaid, Obamacare gives states two options: take more money from the federal government to put more people on Medicaid; or lose the federal funding they were already getting for the low-income health-care program. The Supreme Court ruled that threatening to take away a state’s Medicaid funding unless the state does what the federal government wants is “unconstitutionally coercive” and declared it invalid. Because any given part of a Supreme Court decision can set a precedent for future laws and can even invalidate an established law if it is challenged using the Supreme Court’s new argument, the Medicaid decision could affect the National Minimum Drinking Age Act.

In 1984 Congress passed the law that made it illegal for anyone in the United States under the age of 21 to purchase or publicly possess alcohol. While drinking laws are and always have been a states issue, the federal government was able to enforce the minimum age by making it a part of the Federal Aid Highway Act (PDF). So for 28 years, states have been compelled to keep the minimum legal drinking age at 21 or face losing their federal highway funding.

In 1987 the state of South Dakota, which permitted the sale of beer containing up to 3.2 percent alcohol to 19-year-olds, challenged the law. The case went to the Supreme Court, which decided that it was constitutional for Congress to use the threat of financial penalty to get states to do something, such as enforce a drinking age minimum, as long as the condition under which the penalty is imposed is unambiguous, promotes the “general welfare,” relates to “the federal interest in particular to projects or programs,” and fits within the lines drawn out by the 10th Amendment—which defers all powers to states that are not granted to federal government or prohibited by the Constitution.

The highway funding threat is how the U.S. government has been able to effectively enforce a national minimum drinking age for nearly 30 years. But on Thursday the Supreme Court declared that withholding money from states as a punishment for not doing what the federal government wants is unconstitutional. Federal aides and lawmakers immediately voiced concern that the new stance could reignite such fights as the drinking-age battle, not to mention No Child Left Behind, which also withholds funds from noncompliant states. If a case like the one South Dakota pursued against the drinking age act in 1987 were pursued now, using the health-care decision as precedent, the outcome might be different.