No need. There are now sensors which can passively detect the presence of alcohol on anyone's breath within the cabin, and sensors which can detect BAC when you put your finger on them.

    if alcohol_detected_in_cabin:
        promptDriverForFingerprint()

The same cameras used to monitor if the driver is falling asleep can also check for cheating.

The law only specifies the outcome (alcohol detection) not the implementation (hose blowing)