whose goal is to help telepaths control thier powers, and to regulate telepath behavior to prevent unscrupulous activity toward 'normals
Alfred Bester first introduces this concept in his 1953 novel, The Demolished Man, which explores a world where a small percentage of the human population has developed telepathic abilities. Crime is virtually non-existent, as esper police can detect criminal intent before it happens.
The Esper Guild concept in The Demolished Man is one of the earliest explorations of the societal impact of telepathy. Bester describes an intricate subculture of telepaths, imagining their conversations, games, and politics. He explores the stratification of esper society based on the strength of an esper's ability. He also posits the esper guild as enforcing a code of conduct, for which the punishment is banishment from contact with other espers.
One of the best passages in the book relates an esper party. Bester's love of typographic puzzles shows through in his description of some mental games where telepaths mentally weave sentences like crosswords.
The psi-corps in the Bablyon 5 universe was intentionally patterned on a corrupted version of Afred Bester's Esper Guild.