Since Kazbegi is bordered by different areas its always a good idea to take a passport if you go for a hike. You definitely need one if going to Truso (both trecks) and Devdoraki glacier. Behind Jutta there is also a post, but you don’t pass by if your destination is Chaukli mountains. Usually border gurads where friendly to us. Most of them are locals and know the area very well. So if you pass one of the posts they will register you by writing down passport number, country and your name and tell you how far it is possible to continue.