It's quite open to abuse by recreational users in CA. Note the terms "recommendation or approval" of a physician (not a "prescription").
"Although the Compassionate Use Act allows the use of medical marijuana by a patient upon the recommendation or approval of a physician,
California physicians should bear in mind that marijuana is listed in Schedule I of the federal Controlled Substances Act, which means that it has no accepted medical use under federal law.
However, in Conant v. Walters (9th Cir.2002) F.3d 629 the United States Court of Appeals recognized that physicians have a constitutionally-protected right to discuss medical marijuana as a treatment option with their patients and make oral or written recommendation for medical marijuana. However, the court cautioned that
physicians could exceed the scope of this constitutional protection if they conspire with, or aid and abet, their patients in obtaining medical marijuana.
Medical Marijuana | Medical Board of California
Why the federal government classifies marijuana like heroin
"To initiate a schedule, the DEA first asks if a drug can be abused. If the answer is yes, then it's put on a schedule. If no, the drug is left out. After that, the drug's relative potential for abuse and medical value are evaluated to decide where on the scale it lands.
The two big issues, then, are a drug's potential for abuse and medical value. Congress did not clearly define abuse under the Controlled Substances Act. But for federal agencies responsible for classifying drugs, abuse is when individuals take a substance on their own initiative and develop personal health hazards or pose other risks to society as a whole.
To find medical value, a drug must have large-scale clinical trials to back it up — similar to what the Food and Drug Administration would expect from any other drug entering the market.
There are five schedules:
schedule 1 drugs are determined to have high potential for abuse and no accepted medical use, while schedule 5 drugs are considered to have low potential for abuse and some medical value.
Some examples of the drugs that are on each schedule:
Schedule 1: marijuana, heroin, LSD, ecstasy, and magic mushrooms.
Schedule 2: cocaine, meth, oxycodone, Adderall, Ritalin, and Vicodin……"
Why the federal government classifies marijuana like heroin - Vox