In California, marijuana has gone from being an illegal drug to being big business.

Last week Governor Jerry Brown signed into law three pieces of legislation (AB 243, AB 266, and SB 643) aimed at regulating the $1.3 billion medical marijuana industry in the state. The legislation, collectively called the Medical Marijuana Regulation and Safety Act, will take effect January 1, 2018.

The Act establishes a state Bureau of Medical Marijuana Regulation, which will establish and oversee standards for crop cultivation, licensing, taxation, quality control, shipping, and product packaging in this booming industry.

In 1996, California was the first state to legalize use of medical marijuana, through a voter referendum. The state has not legalized recreational marijuana use yet, but a measure is expected to be on the ballot in 2016.

Wondering where things stand in your state? Here is a summary and handy chart, current as of June 2015.

Common Sense Counsel: If you're an employer in a medical marijuana state, here are a few steps you can take to prevent your workplace from going up in smoke:

• Know the laws that apply to your employees. This includes substance abuse laws but also the Americans with Disabilities Act, and state and local disability discrimination laws.

• Adopt a substance abuse policy that includes prescription medication that may affect employees' ability to work safely and competently.

• Make sure that your job descriptions designate and address "safety-sensitive" tasks.

• Let employees know your stance on medical and recreational use of marijuana.

• Review your substance abuse policy and forms, and update as needed.

• Train supervisors on "reasonable suspicion," with special emphasis on marijuana and alcohol.