According to Workplace Fairness, a national nonprofit that advocates for employee rights, most workers in the private sector are not protected from retaliation for expressing their political beliefs on the job. Most employees in the United States, after all, are “at-will,” meaning they can be fired for just about any reason or for no reason at all. Only certain protected categories — such as race, ethnicity, gender, disability or religion — are protected by federal law.

Public employees typically have far greater protections when it comes to political expression at work. The Supreme Court has ruled — most recently with a decision involving a New Jersey police officer who was demoted for buying a yard sign for a mayoral candidate opposed by his superiors — that public employers cannot discipline an employee for engaging in political activity unless that activity disrupts the workplace in some way.

As is the case with the rights of public sectors to discuss or display their political beliefs, how an employer can draw the line between activity that disrupts the workplace will always be subject to a broad range of interpretation, and no doubt be fiercely debated in cases in which a manager disciplines an employee for what he or she deems disruptive behavior.

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But only a handful of states — New York, California, North Dakota and the District of Columbia — have laws that explicitly protect private sector employees from discrimination on the basis of political affiliation or opinions. Some cities, such as Seattle and Madison, Wisconsin, also have implemented similar laws.

Fewer constraints on private employers

Most private sector employers are free to impose a broad range of restrictions on political expression in the workplace. They can bar employees from wearing political buttons or discussing politics on the job.They can also fire an employee for political beliefs they voice off the job.

In 2004, for instance, an Alabama woman, Lynne Gobbell, was fired for having a John Kerry bumper sticker on her car while working for a boss who was a George W. Bush fan. (That story ended happily for Gobbell, who was rewarded with a job by the Kerry campaign after it was alerted to her story.)

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It is also legal for most private employers to make hiring decisions based on political beliefs. Indeed, there are many private organizations that are explicitly political in their mission and hire only employees who share beliefs that align with their mission. Political parties and political advocacy groups, for instance. The National Rifle Association is probably not inclined to hire those who show up for job interviews with Hillary Clinton bumper stickers, for instance.

A major exception, of course, relates to union organizing. For more than 80 years the federal government has barred private sector employers from retaliating against employees because of union activity, including discussing union organizing with colleagues, attending union meetings or handing out union literature to coworkers as long as these activities don’t interfere with work.

Over the decades, the National Labor Relations Board has rendered a number of decisions regarding how employers may restrict union activity during work hours. According to Lisa Guerin, a labor attorney, employers are allowed to bar employees from discussing nonwork issues on the job, but they are not allowed to single out union activity as the only prohibited topic of discussion.

Workers who do unionize are often afforded additional political speech protections in the collective bargaining agreement, including an agreement from management to not retaliate against workers for engaging in political activities outside of work. This is of course relevant to the case of Kaepernick, who like all National Football League players, is covered by a collective bargaining agreement between the players union and the league.

So could Kaepernick get fired for taking a stand on the national anthem that his boss doesn’t like? The short answer is: in most cases, yes.

But just like the NFL, most employers recognize that firing employees for expressing political opinions might be legal, but it’s not necessarily good for business.