(a) Each certificate holder or operator shall test each of its employees who perform a function listed in subpart E of this part in accordance with that subpart.
(b) Except as provided in paragraph (c) of this section, no certificate holder or operator may use any contractor to perform a function listed in subpart E of this part unless that contractor tests each employee performing such a function for the certificate holder or operator in accordance with that subpart.
(c) If a certificate holder conducts an on-demand operation into an airport at which no maintenance providers are available that are subject to the requirements of subpart E of this part and emergency maintenance is required, the certificate holder may use individuals not meeting the requirements of paragraph (b) of this section to provide such emergency maintenance under both of the following conditions:
(1) The certificate holder must give written notification of the emergency maintenance to the Drug Abatement Program Division, AAM-800, 800 Independence Avenue, SW., Washington, DC 20591, within 10 days after being provided same in accordance with this paragraph. A certificate holder must retain copies of all such written notifications for two years.
(2) The aircraft must be reinspected by maintenance personnel who meet the requirements of paragraph (b) of this section when the aircraft is next at an airport where such maintenance personnel are available.
(d) For purposes of this section, emergency maintenance means maintenance that—
(1) Is not scheduled and
(2) Is made necessary by an aircraft condition not discovered prior to the departure for that location.
ACE rules page: Part 120 in plain English