In an October 20 memo titled "Do Not Compromise Military Operations for Personal Financial Gain," later published by CBS News, he said such wagers could hand enemy countries valuable clues.
The memo went to senior Pentagon leaders, Combatant Command heads, and directors of Defense Department field activities.
He also said financial stakes can distort judgment, noting that a logistician with money riding on a strike date has an interest in that date.
The prohibition covers all financial platforms, including traditional betting services and sites such as Polymarket and Kalshi, and applies whether the information is classified or not.
Violations could bring administrative, disciplinary, or criminal action under the Uniform Code of Military Justice or federal law.
Kalshi and Polymarket both ban insider trading, though criminal charges would likely be a stronger deterrent than losing platform access.
The memo follows several incidents. In April, a US Army soldier was arrested and charged with using confidential information to win $410,000 in Polymarket bets on the timing of the capture of Venezuelan President Nicolás Maduro. An August report from the Anti-Corruption Data Collective identified 152 suspicious wallets that placed longshot bets on military and defense markets and won a combined $8 million. The Associated Press reported that new Polymarket accounts made well-timed bets on a US-Iran ceasefire just before President Trump announced it in April, and the White House warned staff against trading on private information the same day. Meanwhile, the administration is trying to block state regulation of prediction markets, citing the Commodity Futures Trading Commission's exclusive jurisdiction, while courts have split and states are seeking Supreme Court backing for their authority.
