Phillipa Louvois was the Starfleet judge advocate who presided over the hearing that ruled on whether Data had the right to choose.
Captain Phillipa Louvois was the judge advocate general for the sector containing Starbase 173 in The Measure of a Man. She had history with Picard: they had once been romantically involved, and she had prosecuted him in the court martial that followed the loss of the Stargazer.
When Bruce Maddox sought to dismantle Data for study, Louvois first ruled that Data was Starfleet property. At Picard's request she held a formal hearing, with Riker forced to argue against Data. After the arguments she ruled that Data was not property and had the right to choose for himself. Amanda McBroom played her.