This is incorrect in most states.

Employers can require an employee to be “on-call” and available to work on an emergency or as-needed basis. Employers are generally not required to pay employees who are “on-call,” unless the employee is actually called to duty. However, if an employer places significant restrictions on how an employee spends their time while on-call, this time may need to be compensated as hours worked.

The tenth circuit of appeals came up with this test to determine if the employers restriction constitutes on call hours as hours worked.

Where the employee is not required to remain on the employer's premises, the critical inquiry is whether the employee is able to use the time effectively for his or her own purposes. Here, the report requirement necessarily entailed that the employee could not drink alcohol, must be able to dress in uniform, and must be able to travel to the airport, park, and pass through security within one hour of a call. She was not able to make or attend doctors' appointments for herself or her children, do her weekly shopping, nor go on field trips with her children. The court compared these circumstances with many FLSA cases presenting similar, or even more restrictive, circumstances involving availability by pager, inability to drink alcohol, and ability to report within 30 minutes or one hour. In the FLSA cases, it was determined that the employees' activities were not so curtailed as to require the on-call time to be considered compensable working time. The court followed this precedent.