In Wraith: The Oblivion, the Proctors are one of the Guilds. The Proctors are considered a criminal Guild, since their Arcanos, Embody, violates the dictum mortuum by allowing a wraith to cross the Shroud. Relatively little canonical information is available on the Proctors, as no splatbook was ever published for the Guild.
The Guild is organized into a number of local Proctors' Societies across Stygian territory, which take care of such things as contact with the local Hierarchy. Should the need arise, delegates from the Societies meet in the Proctors' Congress in Stygia, which decides on matters that affect the Guild as a whole.
Of the criminal Guilds, the Proctors are the one that has the tightest relationship with the Hierarchy. Unlike the Puppeteer or Haunter Guilds, they have no known exterior agenda about crossing the Shroud - they want to experience life again, and are generally self-absorbed and fairly pacifistic about this. Consequently, the Proctors are largely tolerated by the Hierarchy; if a Legion needs a shroud-crossing job (and they do more often than they care to admit), the Proctors are the natural choice.