Like every measurement device, lidar systems need the possibility to have their results certified according to the criteria of present-day quality assurance. To this aim guidelines are needed. KRdL, the German Commission on Air Pollution Prevention, has been quite active in this field and issued several guidelines on lidar systems and measurements; a few more are actually in preparation. The present paper gives a brief account of the intended purpose, of the procedure followed to get the guidelines written, discussed, approved, and issued, of some of the differences to guidelines for in-situ measurement systems, and of lidar-specific problems and how these problems have been solved. As an example, parts of the guideline "Ground-based remote sensing of visual range - Visual range LIDAR" are presented, emphasizing the difficulties involved when visibility definitions are extended for remote sensing instruments covering a large measuring volume.