The Troll Emancipation Act is mentioned briefly in Everblaze by Keefe. He tries to convince Sophie to ditch her Foxfire sessions, claiming that the Troll Emancipation Act is boring. This event is explained in Elvin History.
Emancipation means the fact or process of being set free from legal, social, or political restrictions, so the Troll Emancipation Act likely was some sort of act of freedom from such restrictions. Trolls are one of the intelligent creatures who signed the treaty with the Elves.