WASHINGTON—Employers recently got additional clarity on the legality of firing employees over social media activities, when a federal labor board ruled that an Arizona newspaper was justified in firing a reporter over the content of messages he was posting to Twitter.

In September 2010, the Tucson, Ariz.-based Arizona Daily Star fired its crime and public safety reporter for repeatedly publishing what the paper deemed to be “unprofessional and inappropriate tweets” via his account with the microblogging platform Twitter, including references to his position at the paper and links to its website, according to an advisory memo the National Labor Relations Board issued last month.

The board found that the unnamed reporter's termination did not violate a provision of the National Labor Relations Act that protects communications by employees as long as they relate to—or seek to involve other employees in a discussion of—working conditions or employment terms. The NLRB has sided with workers in a few previous cases where social media-related conduct was seen as protected.

According to the NLRB's memo, in January or February 2010, the reporter posted a snide remark about the Daily Star's copy editors concerning headlines that had run in the sports section. The paper's editors reprimanded the reporter and told him he was prohibited from “airing his grievances or commenting about the Daily Star” in any public setting.

Several months later, the reporter posted several messages related to his work as a crime reporter for the paper, including tweets intended to be humorous references to Tucson's homicide rate (see box).

On Sept. 21, 2010, a local television news station posted a tweet containing a misspelled word, which the reporter lampooned in a tweet of his own, calling the station's staff “stupid TV people.” The next day, the news station's producer emailed the Daily Star's staff to complain about the “unprofessional” tweet. The reporter was fired on Sept. 30.

The newspaper is owned by Davenport, Iowa-based Lee Enterprises Inc.

While the NLRB stood behind the Arizona Daily Star in its decision, attorneys versed in social media and employee practices litigation say the paper ought to count itself fortunate.

In its advisory memo, the NLRB noted that the Daily Star did not have an internal policy specifically addressing social media, and that the paper could have found itself in violation of the labor relations act after its managers forbade the reporter from publicly airing any grievances he had about the paper.

“I cringe when I read about a human resources manager saying that an employee can't tweet about anything work-related or air his grievances in a public forum,” said Ricki Roer, a partner in the labor and employment practice group at the Manhattan-based law firm Wilson Elser Moskowitz Edelman & Dicker L.L.P. “It's not that the Daily Star got away with one, but that would not be a gross overstatement.”

She noted that the controlling factor in the case was still the reporter's posts, not the paper's lack of a NLRB-compliant social media policy.

“Commenting flippantly about Tucson's homicide rate with links to the articles is something that falls far afield of any arguable protected action,” Ms. Roer said.

The importance of training on the law for employees and management is the key lesson in the Arizona Daily Star case, said Bethesda, Md.-based social media attorney Bradley S. Shear, Bethesda, Md.-based managing partner of the Law Office of Bradley S. Shear L.L.C. Employees need clear boundaries, and employers need to make certain those boundaries are legal. Though neither was a controlling factor in the paper's case, Shear said, “it was close.”

“If you're going to have your employees utilizing a certain medium or technology, you have to give them tools to do that,” Mr. Shear said. “This company didn't do that.”

The NLRB's advisory opinion in the Daily Star case contrasts sharply with at least one other recent decision. The board filed suit against the Buffalo, N.Y.-based Hispanics United of Buffalo nonprofit organization for firing five employees accused of harassing a sixth employee via Facebook. In that case, an employee posted on her Facebook page an allegation that the organization did not do enough to help the organization's clients. Five employees took to the site to defend their job performance and criticized working conditions, which included workloads and staffing issues.

But, as Melinda Reichert of Palo Alto, Calif.-based Morgan, Lewis and Bockius L.L.P. said, the discussion turned nasty and was construed by the managers of Hispanics United as harassment directed at the employee originally mentioned in the post. Ms. Reichert said the NLRB's decision to file a complaint seemed, based on the facts presented in the board's memos, to be at odds with its decision on the Arizona Daily Star case.

“I would argue that if the posts were in fact inappropriate, the employer should be able to discipline for them, as they did in the Arizona (Daily) Star case,” she said.