DUIs are state law, but usually it is ‘being in control of the vehicle.’ That can mean just sitting in the drive’s seat, even in a private parking lot. It happens a lot in the parking lots of bars.
I have actually worked on cases like this. You’d think it was rare, but it is not. There was even an Everybody Loves Raymond episode where Debra fell asleep in her car because she’s had too much to drink and calls for someone to pick her up. Arrested for DUI.