WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Removing/Installing Anti-Roll Bar From Control Arms
Courtesy of VOLVO CARS OF NORTH AMERICA.
Remove the nuts. Lock the ball joint using an open wrench to remove the nut.