​It is illegal to drive after smoking marijuana if it impairs your ability to drive safely.  The prosecutor must prove beyond a reasonable doubt that the marijuana in your system impaired your ability to drive. The evidence used can be a blood test, driving pattern, and physical signs and symptoms tested by a drug recognition expert.

​Yes, both the driver and the passenger can be arrested.  In California, possession can be physical or constructive, so you can be arrested for possessing marijuana even if you are not physically in possession of it.

​Yes, the medical prescription card does not protect you from driving under the influence of marijuana.

​The administrative suspension is 4 months for first time offenders with no injuries to other parties.  The license suspension as a result of the administrative suspension for second time offenders with no injuries is 12 months, and the suspension length gets longer for third and fourth time offenders.  A conviction of a DUI in court will result in a longer suspension period.

​Yes, under California Vehicle Code section 23152(e), driving under the influence of drugs, legal or illegal, is a criminal offense.  If you are the driver of a vehicle and contacted by an officer who suspects you are under the influence of marijuana either due to your admission of smoking marijuana or by observing physical symptoms of drug use, then you can be arrested for DUI.

If you are a California licensed driver, the police, by law, can physically take your drivers license away if you are arrested for driving under the influence of alcohol or a combination of alcohol and drugs.  If you have an out of state drivers license, then the police cannot take that license, and if you are only suspected of driving under the influence of drugs, then the police cannot take your license.