It’s also – in most cases – very wrong.
The EEOC provides some examples where English-only would be justified by business necessity:
For communications with customers, co-workers, or supervisors who only speak English.
In emergencies or other situations in which workers must speak a common language to promote safety.
For cooperative work assignments in which the English-only rule is needed to promote efficiency.
To enable a supervisor who only speaks English to monitor the performance of an employee whose job duties require communication with co-workers or customers.
If you wish to mandate an English-only workplace, we strongly suggest you review the policy with an employment attorney prior to implementation.
It’s not worth it!