They're endangered and all "iconic" and stuff. They ONLY grow in parts of Arizona, New Mexico and Mexico. Still, it is an odd law and it can be a huge pain in the ass for people too! You can't even remove them from your own property if you want to build a house or a barn or something. I THINK that you can pay certain government horticulture/environment people to move them as live cacti, but I'm sure that is insanely difficult considering the size of an adult saguaro and it's very expansive root system.