If I remember correctly--it's pressed on. I broke mine once and had to replace it--thats the best of what I remember though--what are you trying to do--this thing is made of plastic, which means it won't take a lot of pounding when trying to take it off.

it's not a rivet. you just have to pull it off. it is pressed on too tightly to do it by hand--you MIGHT be able to get away with using a vise. the correct way to do it is to use a pulley puller. when i changed my PS pump, Advance auto Parts swapped the pulley for me on the spot using their own puller. I just loosened the 3 bolts for them because i figured that the new pump might not include a pulley.

It usually pops off, but sometimes it will break off. I usually have luck gently prying at it. It is not pressed in.