The U.S. Department of Labor released the final version of a rule today that will force companies to disclose more information about the third parties, including attorneys, that they hire to help counter unionization campaigns.

The so-called “persuader rule,” five years in the making, will require disclosure of the identity, fee arrangement and scope of activities done by a lawyer or consultant who helps management try to persuade workers not to unionize. Aside from creating a new reporting burden and giving away private information to unions, experts say the new rule may threaten attorney-client privilege and even discourage employers from seeking out legal support and advice.