If you mean he can turn around and sue copyright trolls again, he cannot do that. His former clients will claim there is a conflict, since now he has access to their data under attorney client relationship.

Doesn't this work the other way around?

Perhaps not since his previous clients would have been individual cases for disparate individuals and there wouldn't have been so much 'data'?

Real double- and triple- agents laugh at claims of 'conflict' and the rules which bind ordinary agents.