Google employees may find safety in numbers after staging a worldwide walkout on Thursday — but they could be surprised to learn that it’s not the First Amendment that would protect them from corporate discipline.

The First Amendment to the United States Constitution prevents the government from abridging the freedom of speech. Similarly, the state constitution of California, where Google’s headquarters is located, provides, “Every person may freely speak, write and publish his or her sentiments on all subjects, being responsible for the abuse of this right.”

Generally, however, an infringement on speech or a protest can only be unconstitutional if it is fairly attributable to the government. Employees of private companies are often “at will,” which means they can be terminated for no cause. Sometimes workers have a written employment agreement with their employer which spells out acceptable conduct and terms of employment, but often this language favors the employer over the employee. Either way, a person's free speech rights under the federal and state constitutions are not infringed unless there is state action.

This does not mean the Google employees are completely unprotected or that they can be fired for their walkout.

In passing the National Labor Relations Act of 1935, Congress intended to protect private employees when they organize collectively for their mutual aid and protection in the workplace. The NLRA provides that “employees shall have the right to ... engage in ... concerted activities for the purpose of … mutual aid or protection.”

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Google employees stage a walkout over sexual harassment on Thursday in New York. Bryan R. Smith / AFP — Getty Images

The law makes it an unfair labor practice for the employer to interfere with or restrain employees in the exercise of these guaranteed rights. In fact, federal law “expressly foster[s]” a “freewheeling use of the written and spoken word” for employees in certain situations, according to the Supreme Court.

Both union and non-union employees have a right to act for the purpose of "mutual aid or protection." This includes efforts to improve their conditions of employment, even if they use methods outside the immediate employee-employer relationship.

Federal courts have acknowledged that employees who jointly participate in a walkout to present job-related grievances to management are engaged in protected concerted activity, regardless of whether or not the employees are members of a union.

But, if a walkout stops production and is only for the purpose of protesting over a supervisor, it might not be protected by the NLRA.

If Google employees had been only walking out to, say, protest the hiring of a particular supervisor, courts have indicated this might not be protected activity. The choice of supervisors is a management prerogative, one that employees don’t automatically have a statutory right to “bargain” about.

In London, Google employees joined the walkout. Tolga Akmen / AFP — Getty Images

On the other hand, a walkout because that same supervisor's conduct is impairing the conditions of employment would be protected concerted activity.

It’s possible that the Google protests reacting to company action or inaction in dealing with supervisors are unprotected, depending on the specific reason for the walkout.

The law has to walk a line: protect employees’ right to advocate for their protection while also preventing employees from going too far and vetoing any management decision just because it’s unpopular. In the case of managers ignoring complaints or permitting sexual misconduct to occur, courts have suggested that this kind of conduct addresses workplace conditions.

A walkout for this reason is likely protected by federal labor law, even if the First Amendment offers no protection.

Danny Cevallos is an MSNBC legal analyst. Follow @CevallosLaw on Twitter.