On the same day that recreational marijuana became legal in Massachusetts, Boston Police Commissioner William B. Evans said Thursday that police officers will not be allowed to consume pot.

“I know in the Police Department, we’re not going to tolerate anyone having that in their system,’’ Evans said Thursday during an interview on WGBH radio. He said federal law requires that police officers refrain from using marijuana.

Evans added that businesses have the right to tell their employees they don’t allow marijuana use.

“I think it’s probably going to be up to the individual company, and they’re going to have their own rules,’’ Evans said. “I mean with alcohol, if you come in under the influence of alcohol, they’re going to send you home.’’

Evans said the ballot question legalizing marijuana, which passed last month with 1.8 million votes, is “uncharted territory’’ for police officers trying to navigate the legal gray area the initiative presents.

Under the new law, residents 21 and older can purchase, possess, use, and home-grow select amounts of marijuana. However, it is still not legal to sell the drug; retail stores will not be able to sell marijuana until January 2018.

“We’re trying to get educated on it also. It’s so complex,’’ Evans said. “It’s very confusing. I’ve read it about 10 times and I still don’t get it.’’

Evans said arrests for marijuana use have dropped in recent years.

“For the most part, marijuana has been decriminalized for some time,’’ Evans said. “Our concern is it getting in the hands of young kids and getting in the hands of people who are getting behind the wheel.’’

Evans said he is trying to create a training bulletin so officers can learn how to tell if someone is driving under the influence.

“We’ll probably put you through a field sobriety test like we would with someone under alcohol, but we don’t have a breathalyzer,’’ Evans said. “We’ll have to do some research and possibly revisit our field sobriety tests.’’

Olivia Quintana can be reached at olivia.quintana @globe.com. Follow her on Twitter @oliviasquintana.