Yes, they do.
Betters, in order to place a wager, have to agree to the terms of service of the website. Every gambling website I’ve ever known or heard of specifically allows the site to void wagers, even those already accepted. In addition, many states that allow online sports wagering have laws that allow websites to follow their “house rules” that allow negating previously accepted wagers for “obvious errors”.
The betters know what they are getting into and previously agreed to the rules.
And many states protect their citizens against some unfair contract provisions in contracts of adhesion, like this one.
Canceled after the wager is accepted and the event is complete? Or after it was accepted, but before the outcome is known?
"Without prejudice to any other provision in these Rules (including, but not limited to, the Sport Rules), a bet will be voided, totally or partially, irrespective of the bet being settled or Unconditionally Determined, if any of the following circumstances have occurred:
An Error in connection with the bet;
The bet was accepted by DraftKings on an Event that was directly or indirectly affected by illegal or suspected illegal activity. If there are any concerns that an incident that directly or indirectly affected an Event is related to any illegal or suspected illegal activity, DraftKings may withhold settlement of bets on such Event while the concerns are being investigated and/or void bets on such Event;
The bet was accepted by DraftKings after the last instance of play on an Event;
A customer places multiple copies of the same bet or places a series of bets that contain the same or similar Selection(s). When this occurs, all bets will be voided apart from the 1st bet placed. For example only, one Selection is repeatedly included as a leg in multiple Parlay bets (as defined in the Market Rules) where the other legs of the Parlay bets involve Selections with high-probability odds …"
From General Rules.
I could find no cases that have held that any of the major gambling sites’ Terms of Service are unenforceable adhesion contract and thus not binding. Do you have any? The closest I could find (in my admittedly very cursory search) was a California case which held:
“Because Nessim failed to establish substantive unconscionability, the Court finds Nessim failed to establish the arbitration agreement is unconscionable under California law. Laster v. T. Mobile USA, Inc., 407 F. Supp. 2d 1182, 1187 (S.D. Cal. 2005) (“An adhesion contract is unconscionable when both procedural and substantive unconscionability are present.”); As such,
the arbitration agreement is enforceable.”
However, there are states in which the gambling regulators have taken the side of betters. For example, both New Jersey and Massachusetts have forced online gambling platforms to pay off betters despite their claims of “obvious error”.
With the massive increase in online sports betting, I suspect we are only at the tip of the iceberg in regards to these kinds of issues.
I mean, both of those are examples, right?
Neither was a court case, and neither had to determine whether the agreement was an unenforceable adhesion contract. The Massachusetts one was the gaming commission determination that DraftKing’s error in allowing certain parlays was not an “obvious error” that would allow Draftkings to void the bet. The New Jersey one was had the New Jersey’s Division of Gaming Enforcement denying Draftkings’ petition to void bets that had an error made by a 3rd party. They decided that, pursuant to NJ regulations, Draftkings had to pay out even if it was an “obvious error”. Only Connecticut ruled the same, the other 17 states allowed them to void the bets.
I could find nothing to do with “contracts of adhesion” in either.
Thanks @Hamlet. DraftKings reserves the right to void settled bets, but the corresponding Gaming Commission must be informed and they make the decision. For this error Massachusetts and New Jersey rejected the void request and Pennsylvania accepted it.
DraftKings had a similar error in 2023 that was accepted by MGC.
https://sbcamericas.com/2025/12/22/draftkings-mlb-error-millions-payouts/
Would there be yet? It’s still a fairly new industry. The Gaming Commissions rule on the regulations for the bookmakers and the bettors, according to the terms and services, are required to resolve via arbitration.
Maybe if MGC ruled in favor of DraftKings on the Lukes bet the bettor would have enough upside, but it wouldn’t be worth it for most people.
But there’s a difference between wagers already accepted and wagers already resolved. If DraftKings had canceled the bet before the Series, then there might be some folks grumbling that it was a dick move, but legally they’d be 100% in the clear. It’s only refusing to pay out once the gambler had already won that’s a problem.