CHICAGO — Lawmakers made history in Springfield on Friday by passing a bill to legalize recreational marijuana. Governor JB Pritzker has said he will sign it.

Starting Jan. 1, 2020, Illinois residents ages 21 and over can legally purchase and possess up to 30 grams of marijuana.

Employment lawyer Scott Cruz sat on panels in Springfield to discuss what the law would mean for people and their bosses. He said employees may have many misconceptions.

“Employees are going to think, ‘Well, now I can go to lunch, have an edible, come back to work. And my employer is not going to be able to do anything about it,’” Cruz said. “Solving that misconception among employees [will be important]. If we have a ‘zero tolerance’ policy, it means just that: zero tolerance. And if you are impaired or under the influence, we have the right to terminate you and discipline you. … I think employees need to understand that.”

Regardless of state law, marijuana is still illegal at the federal level. That allows employers to ban use among employees.

Cruz compared the substance to alcohol and showing up to work drunk — except marijuana can stay in a person’s system for several days.

“It’s going to be up to the employer to decide if they want to take action based on off-duty conduct,” Cruz said.

But like many people’s perception of marijuana, rules may evolve over time.

“I think some employers will say, ‘Hey, we are fine with that as long as you do it on our own time,’” Cruz said. He noted that jobs that entail safety concerns, like operating heavy machinery, will still require zero tolerance.