The Bolian Isolationists were responsible for the Bolian Isolationist Movement. One of their leaders was Sileon Thall, and the Isolationists lived on New Bolarus until the Vendoth attack on the planet in 2376. (Star Trek: The Cantabrian Expeditions: "Howl")
The Isolationists felt the Bolian government was allowing cultural contamination by involvement with the Federation and reoccurring conflicts with the Moropa.
They left Bolarus IX sometime after 2348 to settle a new planet, keeping their existing traditions in an isolated environment. Sileon Thall's family moved with him to New Bolarus.
Their departure supposedly killed their movement on Bolarus IX, and, by 2376, their xenophobic stance seemed to ease. (Star Trek: The Cantabrian Expeditions: "Howl") Some Bolians seemed unable to forgive the Isolationists or their families for the events taking place during the Isolationist Movement. A good example of this was Cantabrian doctor Akeras Pela's refusal to treat Isolationist leader Sileon Thall's daughter, Starfleet lieutenant Milami Thall in 2372. (Star Trek: The Cantabrian Expeditions: "Oh, What A Lovely War")