Massachusetts is not a signatory. It is the case everyone signed onto

Massachusetts is missing from the list of states that signed the 37-state brief for a simple reason: you do not file an amicus brief in your own case. Massachusetts is the plaintiff. The brief was filed to support it.

Reading Massachusetts as neutral, which a signature list alone would invite, gets it exactly backwards.

Three questions get answered as though they were one

Most state lists you will find are answering a different question from the one in their headline. The three that get run together:

1. Is it lawful for me to trade here? State law.
2. Will the platform let me in? Geofencing, which the platform sets and can change without notice.
3. Am I eligible for the sign-up promo? A marketing offer.

The state legality hub sets out which attorneys general have taken a position on the record, across all fifty-one jurisdictions, and Kalshi legality by state indexes every state with a court record in one line each.

What follows, and where it comes from

Massachusetts did not sign either multistate brief. The rest of this page is Massachusetts specific. Where a claim rests on reporting rather than on a document we read ourselves, it says so at that point rather than in a footnote.

The case the rest of this cluster hangs on

Commonwealth of Massachusetts v. KalshiEx LLC is at the Massachusetts Supreme Judicial Court as No. SJC-13906, with Appeals Court No. 2026-P-244, on review from the Suffolk Superior Court. Those numbers come from the cover of the amici brief, which we read. Every other page in this cluster refers back to this case.

The sequence, as described in law-firm commentary we read

Massachusetts sued in September 2025, alleging Kalshi was evading state sports gambling law. The Superior Court granted an injunction with effect from 8 March 2026. The Massachusetts Appeals Court then stayed that injunction and ordered expedited briefing, and the matter moved toward the Supreme Judicial Court. That sequence is from commentary, not from the docket, and is labelled accordingly.

Why 37 states plus DC lined up behind it

The amici argue that a CFTC designation does not displace state gaming law, running through 7 U.S.C. section 2(e) and the clear-statement rule in Whitman. The full signature block, all 38 jurisdictions, is on the state legality hub. Two of them, Nevada and Ohio, are counsel of record rather than mere signatories.

The attorney general is also being sued by a second operator

Confirmed from a case caption rather than from commentary: Ludlow Exchange, LLC, trading as Novig, sued Attorney General Campbell in the District of Massachusetts on 6 August 2026, docket 1:26-cv-13615. It is one of five such suits Novig filed that fortnight. We read the docket record through the CourtListener API on 20 Aug 2026 and have not read the complaint, so what it argues is not described here.

What makes this the test case rather than one of many

Other states are in federal court arguing preemption, and the results have gone both ways: the Third Circuit affirmed an injunction for Kalshi against New Jersey, while a federal judge in Connecticut held the contracts are not swaps at all. Massachusetts is the state supreme court route, and it is the one 37 attorneys general and the District of Columbia chose to put their names behind.

The provisions in play

Section numbers are given so you can look them up. Where we have not read the provision directly, the sources list says so.

What we could not verify

• Every date in the sequence above. The filing date, the 8 March 2026 injunction and the Appeals Court stay all come from law-firm commentary we read, not from the Massachusetts docket, which we did not retrieve.
• The current posture. We do not know whether the SJC has heard argument.
• The Massachusetts Attorney General's own announcements. mass.gov returned HTTP 403 to us on 20 Aug 2026, so we could NOT read them.
• Whether the Commonwealth has filed anything since 20 Aug 2026.

Questions people actually type

Is Kalshi legal in Massachusetts? There is no yes or no here that would be honest. This page sets out what Massachusetts has actually done, what its law says, and what a court has or has not decided, so you can see the state of play rather than a verdict nobody has issued.

Has Massachusetts taken action against Kalshi? The section above answers this for Massachusetts specifically. Across the country, reporting we read describes fifteen states having sued, investigated or sent cease-and-desist orders over gambling licensure. The states differ, and a page that gives one national answer is flattening that.

Does the CFTC designation settle it? No. Kalshi is a CFTC-designated contract market and nobody disputes that. Whether the designation displaces state gaming law is the contested question, argued through 7 U.S.C. section 2(e) and the clear-statement rule in Whitman, 531 U.S. 457, 468 (2001). Two federal district courts have answered it differently.

Can I be prosecuted for trading in Massachusetts? We are not lawyers and this is not legal advice. The filings we read are about whether the exchange may offer the contracts, not about individual traders. If that is your real question it is one for someone licensed to answer it in Massachusetts.

Is the app blocked in Massachusetts? We have not tested it. Geofencing is a platform setting that changes without notice and is a different question from legality.

How many states are arguing this? Thirty-seven states plus the District of Columbia signed the brief, which is 38 jurisdictions, and Massachusetts is separately the party bringing the case. The full signature block is on the state legality hub.

What this page is not

It is not legal advice and we are not lawyers. It is a reading of public documents and reporting, all linked, so you can check it yourself.