The National Labor Relations Act is typically thought to apply only to relationships between unions and corporations. (It also imposes a duty on unions to deal fairly with their members.) The Act, however, has consequences on non-union companies as well, simply because it protects any employee’s right to form a union where one does not exist. So a company policy in a business that has no union could still violate the NLRA if it could be construed to prevent employees from ever organizing one – or, in the Act’s lingo, if it could prevent them from engaging in “concerted activity.”
A typical example involves the sometimes popular policy of wanting to prevent employees from disclosing their salaries to one another. But any rule that prevents employees from talking amongst themselves, whatever the topic, is a rule that could be seen as discouraging a concerted activity. And such a policy could then be found to violate the NLRA.
Even too broad a statement of at-will employment can create a problem. At-will employment can be changed by mutual agreement in a Collective Bargaining Agreement between a company and a union. So to say that at-will employment will always under any circumstances be the rule could be read to prohibit collective bargaining, violating the NLRA here too. Even the smallest businesses have all that to worry about. Unlike other federal laws that have threshold requirements, like $500,000 in sales for the FLSA (overtime) or 50 employees for the Family and Medical Leave Act, the NLRA starts applying with the first employee.