If only the WT lawyers are to learn the identity of Darkspilver and he gets disfellowshipped-- will the JW lawyers then be in some form of legal contempt?
Only if and when there is evidence that shows the laywer revealed Darkspilver's identity. And even then Watchtower will claim that they have zero influence on the actions and decisions of local elders (perhaps even in a different country), because on paper congregations are independent legal entities.
But if that is the case, the lawyer can be punished, for example with a fine or even being disbarred.