Ba'ku
The Ba'ku are a bunch of nauseating, self-righteous, technology-hating Wholesome Small-Town Folksy People in Star Trek: Insurrection. They inhabit a planet of the same name in an area of space known as the Briar Patch, where abundant metaphasic radiation allows them to live lives free from the burdens of disease and aging (after reaching adulthood). Yet they apparently didn't feel the need to share their great discovery with the rest of the Alpha Quadrant.
At one point, a group of them chose to leave the planet and became exiles known as the Son'a. Forbidden to return, the Son'a began to age and suffer diseases like other humanoids, so they schemed to steal the "metaphasic particles" from those who had exiled them.
Organization
The Ba'ku population is tiny, consisting of only a few hundred known members. While they're governance isn't defined, some kind of communal, participatory democracy seems likely.
Threat Assessment
The Ba'ku are pacifists, so they present no significant threat to other civilizations.