14 CFR § 107.33 - Visual observer.
(a) The remote pilot in command, the person manipulating the flight controls of the small unmanned aircraft system, and the visual observer must maintain effective communication with each other at all times.
(1) Scan the airspace where the small unmanned aircraft is operating for any potential collision hazard; and
(2) Maintain awareness of the position of the small unmanned aircraft through direct visual observation.
The following state regulations pages link to this page.