Local government agencies have begun to warn employees that using recreational marijuana, even off-duty, may violate workplace rules.
Recreational adult-use became legal in 2018 after voters passed Proposition 64 in 2016.
The LAPD circulated a memo to remind officers that drug use on and off-duty is never allowed.
"Department policy is unaffected by the legalization of adult-use marijuana," the memo said. "The use of marijuana or cannabis products for any reason, regardless of duty status, is prohibited."
The memo was signed by LAPD Assistant Chief Jorge Villegas.
LA firefighters were cautioned in December they could be disciplined if caught with marijuana or if they appeared under the influence at work.
"The new law, however, does not change the obligations of City employees to maintain a drug and alcohol free workplace," the Fire Department directive said.
The Metro transit agency said the new law had no effect on regulations for its bus and train operators, as there is a long-standing drug-free workplace policy, and operators are generally required to abide by federal Department of Transportation rules, under which marijuana use is still illegal.
Still, a memo was sent to Metro employees in December.
"Although in California medical marijuana is legal and the sales of recreational marijuana will take effect on January 1, 2018, marijuana remains a Schedule I drug under federal law and is therefore prohibited under Metro's policy."
Los Angeles employment attorney Michelle Lee Flores, who specializes in workplace cannabis issues, said government workers and employees at private firms may be required to follow rules that extend into their private lives and time.
"Employers, whether they be governmental or private sector employers, have the ability to establish rules as long as they're compliant with the laws," she told NBC4.
Even if the agencies already have standing drug-free rules she said agencies should issue a formal notice.
"Employers and employees would benefit from just bringing up the subject, just like the memos that have come out recently," she said, as an employee's acknowledgment of receiving such a notice could be a key factor if there's a violation.
The LA Department of Water and Power said it expects a recreational marijuana warning to be issued soon to employees.
Other agencies, like the LA Unified School District, said existing drug-free workplace rules are sufficient.