Senators voted unanimously on April 30 to bar themselves and their staff from trading on prediction markets, an immediate amendment to Rule 37 introduced by Ohio Republican Bernie Moreno after months of insider-trading concerns over senators wagering on policy outcomes they themselves were shaping.
The US Senate voted unanimously on Wednesday to ban its own members and their staff from trading on prediction markets, an amendment to the Standing Rules of the Senate that took effect the moment the gavel came down. Senate Resolution 708, introduced by Ohio Republican Bernie Moreno, prohibits any agreement, contract or transaction that depends on the occurrence of a specific event — language drafted to capture event contracts on Kalshi, Polymarket, ForecastEx and any platform that emerges to compete with them.
The vote went through under unanimous consent, which means no senator publicly objected. That outcome is more interesting than the rule itself. Prediction-market platforms have spent the last eighteen months arguing that their contracts are a legitimate form of price discovery, indistinguishable in mechanics from commodity futures and protected by the same federal regulatory regime. The Senate just declared, on a voice vote, that the contracts pose a sufficient insider-trading risk that lawmakers cannot be trusted to participate in them. Both things cannot be true.
What pushed this to the floor was the volume of public reporting on senators and staffers wagering on bills, nominations and policy outcomes whose timing they personally controlled. The Padilla amendment, attached to Moreno's resolution before the vote, broadened the prohibition to capture staff and to remove a carve-out that would have allowed blind-trust trading. Effective immediately means exactly that — any open Kalshi or Polymarket position held by a sitting senator or covered staffer was non-compliant the moment the resolution passed.
Enforcement is the part nobody is talking about. The resolution amends Rule 37 of the Senate's Standing Rules, which is enforced through the Senate Select Committee on Ethics. That committee has historically been slow, deferential and opaque, and its sanctions tend to land years after the conduct in question. Whether a Rule 37 violation produces a public reprimand or a quietly negotiated divestment will depend on which committee staffer picks up the file. The deterrent value of the rule is real, but it is also asymmetric. A senator running for re-election fears the news cycle more than the ethics letter.
The platforms themselves had no warning. Kalshi and Polymarket together host the bulk of US-domiciled event-contract volume, and both run know-your-customer onboarding tight enough to identify a sitting senator at signup. Whether either company actively blocks members of Congress is an open compliance question that Moreno's resolution has effectively forced. It would be a strange posture for a CFTC-regulated venue, and Kalshi is one, to keep accepting orders from individuals the Senate has just told to stop trading.
The state-level pressure on the same platforms continues. Wisconsin's attorney general filed suit in April against Kalshi, Coinbase, Polymarket, Robinhood and Crypto.com, arguing that sports-related event contracts amount to unlicensed gambling under state law. The federal CFTC framework that prediction markets rely on is supposed to preempt state suits like Wisconsin's. The Senate's vote complicates that argument by handing state attorneys general fresh ammunition. If the Senate considers these contracts dangerous enough to ban its own members from trading them, why should a state have to permit them?
Polymarket sits in a more delicate spot than Kalshi. It serves US users through a CFTC-licensed wrapper but recently ditched bridged USDC for its own native stablecoin — a structural choice that buys liquidity and creates a fresh surface for regulators to question. The platform also handles the Maduro contract that a US soldier wagered $33,000 on while participating in the raid the contract concerned. Each new headline of that kind makes the Senate's vote easier to defend politically and harder to ringfence to congressional staffers alone.
What S. Res. 708 doesn't reach is the executive branch and the House of Representatives. Federal employees can keep trading. House members can keep trading. The Padilla amendment was drafted to apply only to the chamber that adopted it, because no chamber can bind another by rule. Either the House passes its own version or new federal legislation extends the prohibition government-wide. Moreno is the freshman senator who introduced the rule. The harder vote, a statute that reaches the Treasury Department's mid-level analysts and the Department of Defense's procurement officers, is somebody else's problem.
