The U'lanna Commonwealth was the government of the U'lanna species at the time of its extinction.
It was the owner of a rogue astro-miner in the Idlewild system, destroyed by the efforts of the IKS Pterodactyl-of-Prey and the Stoneship. Also, it had enemies from within, coming under the form of the U'lanna Rebel Alliance. (Star Trek: The Stoneship Files: "A Knight without Armor")
In its heyday, the Commonwealth covered territory that extended deep into contemporary Talarian Republic territory. (Star Trek: The Stoneship Files: "For a New World")