It is not possible to setup area rules in PADS.
Despite many users have voted for this on Mentor Ideas.
However - if you have the Advanced Rules Options, it is possible to setup component and/or decal rules.
Note that these rules only apply in PADS Router - not in PADS Layout.
I create macros to swap between two sets of design rules, one for the design and one for the BGA area.
Saves bags of time, and my sanity.
It's a PITA but Mentor will never allow PADS to approach the functionality of Expedition.