Without getting too bogged down in the details, the UIEGA prohibited banks from facilitating financial transactions to what they called illegal gambling operations.
The UIEGA is the provision (snuck into a terrorism-related port bill at the last minute in the fall of 2006), that led to the destruction of the online poker boom in the United States. It’s called the UIEGA, or the Unlawful Internet Gambling Enforcement Act of 2006. Playing daily fantasy football on Draftkings is legal in almost all states