Article 139 Duty of person in charge to satisfy himself as to competence of controllersI1
United Kingdom
The holder of an approval under article 138 must not permit any person to act as an air traffic controller, or to act as a student air traffic controller, in the provision of the service under the approval unless—
(a)
such person holds an appropriate licence; and
(b)
the holder is satisfied that such person is competent to perform the duties commensurate with the provision of the service.