Thursday’s Supreme Court ruling, which upheld the individual mandate clause of the President Obama’s Affordable Care Act, included a citation by Justice Ruth Bader Ginsburg of an amicus brief co-authored by Wendy Parmet, the associate dean for academic affairs and a George J. and Kathleen Waters Matthews Distinguished University Professor of Law in the School of Law. Parmet has served as the counsel of record for a group of Massachusetts health-care advocates who have argued that the state’s health-care reforms cannot reach their full potential without federal assistance.

What is the purpose of an amicus brief, and what was the intention of the one you filed with the court?

Usually an amicus — or “friend of the court” — brief is an opportunity to provide arguments and points of view that the litigants themselves don’t have the opportunity to make. When you’re representing the parties in a case of this import and complexity, you have to make hard decisions about what you can argue and what you can’t. One of the things an amicus brief can do is open doors and expand on arguments that the parties may not have the space for.

In our brief, we brought the Massachusetts perspective. We said Massachusetts already has a mandate but that even though our mandate is very successful, this is an interstate issue and that federal government really needs to play a role. Even with our mandate, our state is not able to achieve full coverage and realize full cost control because of out-of-staters who obtain health care here. We are not able to put up a wall on our borders and keep out-of-staters from getting uncompensated health care here, so we have to deal with their costs.

We have a lot of commuters, tourists and others who come from all over New England — all over the country — for our hospitals. And many of our hospitals on the borders serve communities that go across state lines. The overall theory that by ensuring everyone in the state and paying less by reducing the cost of uncompensated care doesn’t work as well as it should because our hospitals and providers don’t just serve Massachusetts. States cannot go it alone — it’s an interstate issue.

What are your thoughts on the component of the ruling that states cannot be compelled to expand Medicaid overage to those people in poverty or near poverty?

I think it’s tremendous that this decision means the ACA can move forward. But the court’s decision on Medicaid was surprising, troubling and shocking.

It was surprising because not a single lower court had found merit in the states’ Medicaid claim, and it’s troubling because it casts a doubt about how many of the 16 million people who were going to receive insurance through Medicaid will now do that. The fear is that some of the states that challenged Medicaid — states that have very skimpy Medicaid programs and have very high rates of people without insurance — may choose not to do it on principle, even though the federal government is going to pay for most of the program’s expansion.

The irony and the tragedy is that the poorest of the poor among us — the least well off — are the ones who may not benefit from this act. It will mean people will continue going to emergency rooms with conditions that were preventable or easily treatable early, but are now far worse off than they otherwise would have been.

What legal questions does Thursday’s ruling raise?

It’s very hard to understand the rationale for why states can opt out of a federally-mandated program and how it fits into other instances in which the federal government gives money to the states, whether in special education or the environment or No Child Left Behind. It’s very common for the federal government to provide funds and then expect the states to carry out a program — it really is the way the federal government has operated for the past 75 years.

It is very disturbing because it will invite people who don’t like our special education rules or civil rights laws or environmental regulations to challenge those programs in court.