In labor law, a strike is a collective and organized cessation or slowing of work by employees in order to try to force an employer to accept their labor demands. Strikes can be conducted for a lawful purpose, such as to obtain economic changes like improved working conditions or higher wages from an employer. These are known as economic strikes, and while the strikers cannot be fired, they can be replaced by bona fide permanent replacements.

However, there are instances in which a strike is unlawful. For example, a strike that is in support of a unions commission of an unfair labor practice or a strike that would trigger the commission of an unfair labor practice by an employer might be a strike to achieve an illegal purpose. In such cases, the striking employees can be discharged or otherwise disciplined.

Employees who strike for a lawful object fall into two classes: economic strikers and unfair labor practice strikers. Both classes continue as employees, but unfair labor practice strikers have greater rights of reinstatement to their jobs.