Camping in Shirvan, Ag Gol or Absheron National Parks is almost certainly forbidden as you register at a gate and will be expected to leave by closing time unless you have arranged permission to camp/stay with the authorities. Alti Agach, Shahdag, and Hirkan National Parks are contrastingly huge and contain whole villages so it would be essentially impossible to stop people camping, whatever the technicalities. Note thet one is now supposed to prepurchase entry tickets online for the main National Parks. That works for some but not for others and the Goygol NP seems to remain closed to regular visitors.