An unfair labor practice, or ULP, is an action by an employer or a union that violates workers' rights under labor law. For most private-sector workers, those rights come from the National Labor Relations Act (NLRA), and the National Labor Relations Board (NLRB) enforces them.

The NLRA protects your right to engage in "concerted activity." That means acting together with coworkers to improve wages, hours, and working conditions. It includes forming or joining a union, but it also covers non-union workers who discuss pay, sign a petition, or raise safety concerns as a group.

Here's how a ULP differs from a grievance: a grievance enforces your union contract, while a ULP charge enforces the law. You don't need a union or a contract to file a ULP charge.