[EricH]

Not in the rules, unless <G27> applies. The Updates are silent on the matter.

I'm going to explore <G27> a bit. Here it is:

<G27> HERDING TRACKBALLS – ROBOTS may HERD one or more TRACKBALL at one time.
ROBOTS shall not HERD a TRACKBALL while also being in POSSESSION of a second TRACKBALL. A PENALTY will be assigned for each infraction.

Now, the definition of Herding:

HERDING: Controlling the position and movement of a TRACKBALL while the TRACKBALL is not supported by any ROBOT (i.e. supported by the TRACK or other TRACKBALLS) shall be considered HERDING. Both continuous and intermittent contact between the ROBOT and TRACKBALL are permissible methods of HERDING. E.g. bumping, plowing or dribbling a TRACKBALL around the TRACK are all considered forms of HERDING.

Hmm...Controlling the motion is mentioned as being one thing that constitutes herding. I'm not so sure that the motion is controlled, but...

I'd say it sounds like an interpretation of <G27>. Admittedly it's a little stretched. The only question is whether or not the GDC would support it.