Blood alcohol content does not, by itself, determine whether someone's driving will be impaired by alcohol. Some people may be impaired at a relatively low percentage, while others may be able to drive safely with a relatively high BAC. But regardless of actual impairment, drivers may not lawfully drive in California once their BAC exceeds a certain level. This amount is sometimes referred to as California's “legal limit” for alcohol - also known as the “per se” DUI limit.