State Rep. Phyllis Kahn (D) is a Minnesota institution. The 21-term lawmaker has a PhD in biophysics from Yale as well as an MPA from the Kennedy School at Harvard. In the 1970s, she reformed the state’s laws to demand gender equity in sports programs from college all the way down to primary school.

“She’s known as the mother of Title IX here in Minnesota,” said state Rep. Joe Atkins (D), admiringly. “She’s one of my favorite legislators. But she also drives me crazy sometimes. She likes to push the envelope with certain ideas.”

Ideas like this one: For over a decade, Kahn has been trying to reform the state’s laws on underage drinking. She believes that people 18 and over should be served at bars. It’s safer and would provide an alternative to the unsupervised — often dangerous — drinking that goes on at college campuses.

The policy has gained fans among many university presidents. But the bill has been a tough sell in Minnesota. For years, Kahn has had trouble getting her idea heard before a committee.

Now, she has a new argument up her sleeve that involves Obamacare, the Supreme Court and constitutional law.

Let’s back up for a moment. President Ronald Reagan is the reason why the drinking age is 21 everywhere these days. In the 1980s, nearly half of states still allowed residents to buy alcohol at age 18. In 1984, Reagan signed a bill demanding that all states raise their drinking age to 21. There was a threat: If states didn’t comply by 1987, they would lose 10 percent of their federal highway construction dollars.

Some states didn’t like being pushed around like that. The legal fracas that ensued left us with a landmark Supreme Court decision. The federal government is allowed to attach conditions on the money that it gives states, the court ruled, but there are limits. The feds, for instance, can’t be too coercive. The court said that Reagan was in the clear, though, since federal highway dollars are only a tiny percentage of state budgets.

This decision, South Dakota v. Dole, came to prominence again during the Obamacare lawsuit that came before the Supreme Court in 2012. The  court upheld most of the Affordable Care Act, but it struck down one of the law’s threats. As it was written, the ACA would have taken away federal Medicaid funding entirely from any states that didn’t play along with expanding Medicaid.

Chief Justice John Roberts argued that to bargain with existing Medicaid dollars crossed a line drawn by South Dakota v. Dole. Unlike federal highway funds, Medicaid is a huge chunk of state budgets, about one-fifth of expenditures. More than half of that money comes from the federal government. For the feds to use Medicaid funding as a bargaining chip represented too much of a threat, according to Roberts. Famously, Roberts called this part of the ACA “a gun to the head” for states.

Ever since South Dakota v. Dole, states have been reluctant to lower the drinking age because they would lose 10 percent of federal highway dollars. That threat has always stood in the way of Kahn’s efforts in Minnesota. But she argues that the Obamacare decision, NFIB v. Sibelius, changed the game. She says there’s a chance that Minnesota — and all states — would get to keep their highway money even if they lowered the drinking age.

Really, though?

Kahn said she hadn’t consulted any legal experts yet, but some of her colleagues also seemed to think that this argument could have merit. The Minnesota House commerce chairman, Joe Hoppe (R), told the Pioneer Press Thursday that he’d put it on the committee calendar.

Here come the rain clouds for that parade. Several law professors said that Kahn’s interpretation of the law probably won’t hold up in court.

“I don’t think they have much of a case at all,” said Sam Bagenstos, a law professor at the University of Michigan. The Obamacare decision, he explains, hinged on how important Medicaid funding was to states. “It was explicitly based on the unprecedentedly large size of the threat,” he said.

Whereas federal Medicaid spending makes up over 10 percent of state budgets, the highway money is a pittance, less than one percent. To take away 10 percent of that is a smaller sum still. It’s exactly because that is such a small amount that Reagan’s drinking age bill was allowed to stand some 30 years ago.

“There was not a hint in the opinions in NFIB that would question the holding in Dole,” said Mitchell Berman, a law professor at the University of Pennsylvania.

“I still think the small amount of funding at stake negates a coercion argument,” Nicole Huberfeld, a law professor at the University of Kentucky, wrote in an e-mail.

David Orentlicher, a professor of law at Indiana University, pointed out that a challenge to South Dakota v. Dole would result in dramatic upheaval. The federal government attaches conditions to all kinds of funding, from health care to education to transportation.

No Child Left Behind is an important example. Louisiana Governor Bobby Jindal filed a lawsuit last year against the federal government asking to strike down the law. One of his arguments is that NCLB makes states jump through too many hoops to get federal education money. (Georgetown law professor Eloise Pasachoff has argued that the federal education laws are probably safe from these kinds of lawsuits.)

Orentlicher predicts that the Supreme Court would be reluctant to take away this important tool for making policy at a national level. “That would be a huge limitation on federal powers,” he said.

Oh, well — it was an interesting idea, at least. Atkins, the Minnesota representative, said that the bill was doomed anyway because constituents just don’t want to lower the drinking age. “I don’t think this stands a snowball’s chance in well, let’s say Florida,” he said.