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?

  • 5
    It hasn't reached the Supreme Court yet, but the recent recent antitrust suit against Facebook included 46 states + DC and Guam.
    – divibisan
    Commented Dec 10, 2020 at 18:52
  • @divibisan: I don't see mentioned in there why it might reach SCOTUS. Commented Dec 10, 2020 at 18:59
  • @Fizz If Facebook loses and gets ordered to sell off assets, it's pretty much a 337% guarantee it'll get to SCOTUS, because no way in a frozen-over hell inside another frozen-over hell would Facebook ever do that without exhausting every legal recourse. Of course that's still hypothetical, but a "might reach" scenario is clearly easily conceived. Commented Dec 11, 2020 at 6:06
  • 1
    @Sjoerd: those are not all requests to join as a party, some are amicus briefs. Commented Dec 11, 2020 at 17:38
  • 1
    @zibadawatimmy the supreme court agrees to hear a very small percentage of the cases that it is asked to hear. Of course Facebook would appeal to the supreme court if they lose, but that doesn't mean that the supreme court is likely to hear the case.
    – phoog
    Commented Feb 3, 2021 at 4:54

1 Answer 1


If you include amici curiae, 46 states (and D.C.) were involved at some point in California v. Texas, which was argued before the Court in November. 40 states (and D.C.) were parties to the case at some point or time.

Eighteen states are suing to have the Affordable Care Act struck down entirely: Texas, Arizona, Utah, North Dakota, South Dakota, Kansas, Nebraska, Indiana, West Virginia, Louisiana, Arkansas, Missouri, Tennessee, Mississippi, Alabama, Georgia, South Carolina, Florida

Two states originally sued, but withdrew from the case when their Republican governors lost election and became amici curiae for the defense: Wisconsin, Maine

Sixteen states (and D.C.) successfully petitioned to defend the ACA in court: California, Washington, Oregon, Minnesota, Illinois, Kentucky, Virginia, Hawaii, North Carolina, New York, Vermont, Massachusetts, Rhode Island, Connecticut, New Jersey, Delaware, D.C.

Four states later joined the ACA defense: Iowa, Nevada, Colorado, Michigan

Four states were never parties and are amici curiae in the ACA's defense: New Hampshire, Pennsylvania, Maryland, New Mexico

Two states are amici curiae on neither parties' behalf: Montana, Ohio

The only four states who haven't staked out some sort of position are Alaska, Idaho, Wyoming, and Oklahoma. Not sure if this the record, but it's at least a contender.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .