The Idaho National Laboratory is no longer accepting Idaho driver's licenses for identification because they don't meet federal security requirements.
INL spokeswoman Misty Benjamin tells KIFI-TV that those doing business with or visiting the eastern Idaho nuclear facility will have to bring a U.S. passport or one of about five other accepted identifiers.
The policy started Monday.
Idaho driver's licenses won't work because Idaho lawmakers prohibited the state from implementing the Real ID Act of 2005, passed in the aftermath of the 9/11 terrorist attacks.
The Real ID Act is meant to make it harder for terrorists to use fake identification.
Besides nuclear sites, people using Idaho driver's licenses can also be denied access to federal facilities and commercial flights.