A more thorough explanation:

The Worker Adjustment and Retraining Notification Act (WARN) is a law that requires certain employers to give notice to their employees and government officials when they plan to lay off a large number of employees. This law was passed in 1988.

For example, if an employer with 100 or more employees plans to close a plant and lay off more than 49 employees, they must give their employees 60 days' notice and notify government officials and unions. This law only applies to employees who work at least 20 hours a week and have worked for the employer for at least six months within the last year.

WARN also applies to mass layoffs from other large employers. If an employer plans to lay off 500 or more employees, they must follow the WARN requirements. If an employer plans to lay off 50-499 employees and this makes up 33% of their employees, they must also give WARN notifications.

If an employer does not follow the WARN requirements, they may have to pay their employees back pay for every day the warning was owed. The employer may also face daily penalties from government agencies that were not warned.