Enabling storage devices for certain users

[Cajus Pollmeier]

Hi,

I need to hide USB storage devices for all users by default and show them for 
a couple of users by policy. Well, ok - hide is not enough: it shouldn't be 
possible to mount them via hal except for a couple of defined users.

Is it possible to achieve this by my policy/preferences.fdi file? I wasn't 
able to find a match for the calling uid right now...

Thanks,
Cajus