A pilot wishing to tow advertising banners must hold a Sport Pilot Licence, but does not need a Commercial Pilot Licence . In addition, he must undergo training by a microlight instructor who is authorised to tow banners, and make five banner tow flights under supervision.
Link to the technical requirements of the German Aero Club:
Three-axis microlights can be certified to tow banners as part of a "type inspection" or supplementary type inspection. Particular attention is required not to exceed the permissible limits for weight and the position of the centre of gravity during the tow. skygraphics will assist the manufacturer on request.
There is an up-to-date list of the microlight planes which have already been certified for banner towing on the German Aero Club's website:
Download Requirements for UL-Pilots