It was only a matter of time before the legal landscape protecting employees’ activities confronted an employee’s use of Facebook, which now has more than 500 million users.

This month, the National Labor Relations Board (NLRB) filed a complaint against an employer that terminated an employee who wrote on her Facebook profile, “love how the company allows a 17 to become a supervisor.” The employer is an ambulance service and “17” is the company’s lingo for a psychiatric patient. The employee’s Facebook posting about the supervisor drew supportive comments from her co-workers on Facebook. The NLRB also took issue with the employer’s policy prohibiting employees from making “disparaging” or “discriminatory” comments when discussing the employer, the employee’s superiors, or other co-workers.

The National Labor Relations Act (NLRA) protects employees, both union and non-union, who engage in “concerted protected activity.” For example, complaints about small wage increases among employees voiced directly to management are protected activity.