Laws are enacted to prevent any abnormal behavior that may harm self and others, either physically or psychologically and to protect citizens from being harmed similarly. The one such law that governs such behavior is DUI laws. The law doesn't prohibit an individual from drinking nor from driving. But Driving Under the Influence (DUI) of alcohol or drug is a criminal offense that attracts punishments. According to the National safety Council, there are 12 million auto accidents in the US and 40% of the fatalities are due to drinking and driving.

In California, DUI is governed by two basic laws. They are found in Vehicle code sections 23152 (a) and 23152 (b). They are commonly known to California lawyers as "a" and "b" counts. The first section relates to driving under the influence of alcohol or drug and the second section relates to the threshold limit of alcohol present in the body established through different means such as blood level.

The first section states that "it is a misdemeanor to drive under the influence of alcohol and/or drugs". The code implies the level of deviation of a person's ability, whose mental and physical faculties are impaired under the influence, to drive when compared to that of a sober person under similar circumstances. This is the legal standard of interpretation of the first person.

The second section states that "it is a misdemeanor to drive with .08% or more of alcohol concentration in blood or breath". The second section implies that, even if the person's faculties are not impaired so that the person exercises full control while driving, it is still an offense to drive with a minimum alcohol level in the body.

Although there are two sections, DUI law is only one law and therefore, the punishment is for only one offense, but an individual can be booked under any of the two sections. Besides the basic laws, there are statutes related to DUI such as felony, prior convictions and injuries and manslaughter. Vehicle code 23153 invoked when DUI results in injury to other persons. When deaths are involved due to DUI, the case is tried under Penal code 191.5 and 192. Prior convictions provide for greater degree of punishments for repeat offenses.