Sometimes US Supreme Court cases have had more than one US state as a party, e.g. in Massachusetts v. EPA
The petitioners were the states of California, Connecticut, Illinois, Maine, Massachusetts, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont and Washington [plus some cities, organizations, and Washington DC].
I've counted 12 states there, not including DC. Also
Respondents were the Environmental Protection Agency, [...] and the states of Michigan, Alaska, Idaho, Kansas, Nebraska, North Dakota, Ohio, South Dakota, Texas, and Utah.
That seems to be 10 states on the opposing side, so 22 states were party to the case on one side or the other.
Basically, I'm trying to find out if there are there US Supreme Court cases (that were granted certiorari) and that had a higher number of US states as parties. So, what's the Supreme Court case with the highest number of US states parties to it (not necessarily all on the same side)?
To make this question a little more interesting and answerable, if Massachusetts v. EPA turns out to be the case with the highest state count among the parties, what's the case with the 2nd highest such count?