Social media may be relatively new, but the argument about what employees are allowed to say about employers stretches back more than a century.

The town of Fairfield has found itself in the middle of that debate, which after a few relatively quiet decades is raging again, fueled by technology and varied definitions across society of what is public and what is private. The outcome in Fairfield, where the social media policy has been suspended pending further review following criticism from the American Civil Liberties Union of Maine, will be instructive to the many other public institutions that surely operate under similar rules.

Fairfield’s social media policy, a five-page, 1,700-word document based on a model policy from the International Association of Chiefs of Police, lays out standards for how employees should act online. In a letter to the town on Tuesday, the ACLU said the policy was in parts too broad and too vague, and an infringement on the First Amendment rights of town employees. One section, the group said, could be read to prohibit the criticism of government activity.

For many years, the courts held that governments could fire employees for speech of any kind, under the idea that the workers could leave if they were unhappy. In a case typical of that philosophy, Massachusetts’ highest court in 1892 ruled against a police officer who had been fired for working on a political campaign. The officer had a “right to talk politics,” said Justice Oliver Wendell Holmes, “but he has no constitutional right to be a policeman.”

That changed in 1968, when the U.S. Supreme Court ruled in favor of an Illinois school teacher who had been fired for writing a letter to the editor criticizing his district’s use of public funds. Subsequent rulings have established that the speech of public employees is protected as long as it is in relation to a “matter of public concern,” according to the First Amendment Center.

That can be a tricky standard. It is clear that public employees can speak out as concerned citizens on a matter of public policy. When they speak as an employee, however, or in a way that may disrupt the workplace, the waters are muddied.

In the private sector, employees are not under the protection of the First Amendment, which applies to government interference.

In a series of recent rulings, however, the National Labor Relations Board has sided with private-sector employees who have criticized their employers online, as long as it is part of a concerted effort to improve work conditions.

That means a group of co-workers griping about a boss on a Facebook page is likely protected, while a single employee doing the same to friends may not be.

The rulings from both the court and the labor board leave a lot of room for interpretation. It is unclear, for example, where the courts would fall on the case of Susan Varney, who said she was fired from her job at a Fairfield public library for comments she made online. Would her statements against co-workers and management be seen as disruptive to the workplace? Or would they qualify as protected speech about public policy, given the comments were made under an article about the burdens of low wages?

More of these cases are bound to come forward, as more and more conversations once held on the phone or over coffee are conducted online. Social media has the effect of giving these public conversations the illusion of privacy while reaching far more eyes. Many people also are under the mistaken belief that using a personal account provides them protection from reprisal.

Policies, in both the public and private sectors, must be comprehensive and exact, to clearly spell out what is acceptable and what is not in regard to online behavior. And employees and employers both have to get more comfortable with some interactions being played out online.