As far as I know, anything that comes close to a minor faction as a pirate faction you have to look for 'independant' outposts. Some even fly the pirate 'skull' on or around their stations. I have never seen a 'pirate' faction have control of a system, nor operate from a full on station. but I haven't been everywhere.
If you like you can join the Archon power in PP. That is the largest, in-game pirate group. Also, you could join one of the pirate player groups out there. The code is pretty prevalent out there, and I understand they are recruiting.