I have a Colt a2 Sporter II and I am very curious on if this is a pre or post ban AR?

I do not know that much about what that means but I hear it used a lot. Also, does anyone know if I can put a new upper on it such as a DPMS upper? I really want to get a 1 in 9" bull barrel rather than the 1 in 7" that is on there. I know there is some talk about Colt's pins being bigger but I do not really understand all of that. Thanks guys!