The Baltimore Police Department had been in the process of creating a new social media policy as well, but that effort has been tabled as the new commissioner, Anthony W. Batts, transitions into his role.

The new Fire Department policy applies not just to social media platforms like Facebook but also to chat rooms, online forums and all forms of "electronic communication" other than personal email services and private messaging functions. But the department will not routinely monitor social media accounts of firefighters, the policy states.

Hudson, the First Amendment scholar, said he appreciated that department officials "recognize employers shouldn't be the social media police and go around snooping at employees' social media."

State law bans employers from asking for employees' social media user names and passwords.

Michael Campbell, president of the fire officers union, said the new policy infringes on First Amendment rights and doesn't reflect many of the changes recommended by the unions before negotiations ended.

"The Fire Department said, 'We're going to do what we want to do. It's our way or the highway,' " Campbell said.

"The Fire Department is definitely overreaching," he added. "They're just throwing the kitchen sink out there and seeing what they can get away with."

Clack said department attorneys and the unions went "back and forth for months" on the policy, and the department did incorporate many suggestions from the unions. But eventually, both parties agreed they were not going to reach a consensus, and the department decided to move forward, he said.

"I think in the end, the unions felt like they couldn't support a policy 100 percent because a lot of their members use social media," Clack said.

Clack acknowledged the policy's far-reaching scope but said he will take a more narrow approach to enforcing it. He noted: "It's certainly not my intent to fire anybody."

"Attorneys, when they get ahold of this stuff, try to throw everything in and cover every base, but I'm going to be most interested in people when they're working," he said.

Shear, the social media attorney, said one of the most troubling aspects of the policy is that it's retroactive.

Union contracts prevent the department from punishing employees for actions after a certain amount of time has passed, but Shear said the language of the policy could be understood to allow the department's good-judgment standard to be applied to social media posts made years ago. "It essentially holds you accountable for things in the past, including things you might not be proud of in college or high school," Shear said.

"You've got to be careful regulating speech with public employees, and the way the policy is written, it appears to violate the principles of free speech," Shear said.