Unless it has changed recently - because of the legal competence of EASA to provide such regulations - for the JAA States it is covered here:
JAA Administrative & Guidance Material Section Two: Maintenance Part Three: Temporary Guidance
LEAFLET NO. 38: AUTHORISATION OF FLIGHT CREW PERSONNEL TO ISSUE CERTIFICATES OF RELEASE TO SERVICE FOR MAINTENANCE.
1. Note.
Please be advised that the material contained in this leaflet is either an acceptable means of compliance (AMC) or interpretative and explanatory material (IEM) as stated in JAR-145 Section 2 para 2.4. However because the material has NOT been subjected to the FULL FORMAL NPA process it is possible that the content may change in due course when transferred to JAR-145 after NPA. This means that any organisation using this material to satisfy JAR-145 compliance may have to adjust their processes and procedures as a result of the NPA.
Here is an example - from the TGL - of tasks that can be carried out once authorised:
Holders of a valid JAR FCL ATPL or CPL on the aircraft type may only exercise this limited certification authorisation privilege when performing the duties of a flightcrew member, whilst operating away from a supported location and subject to the need for such authorisation being agreed by the JAA-NAA.
Typical tasks that may be certified and/or carried out are minor maintenance or simple checks included in the following list;
a Replacement of internal lights, filaments and flash tubes.
b Closing of cowlings and refitment of quick access inspection panels.
c Role changes e.g. stretcher fit, dual controls, FLIR, doors, photographic equipment etc.
d Repetitive ADs as specified in JAR 145.30(g)4
e Any check/replacement involving simple techniques consistent with this TGL and as accepted by the JAA-NAA
Jim