Colonies Inside the Federation
The vast majority of Orion worlds are within Federation space, by virtue of both accident, and signature of the Treaty of Rigel on Stardate 48291.44, admitting 39 Orion worlds en-masse to the Federation as associate members, and Rigel specifically as a full member.
All of these worlds were originally founded as an Orion Colony and retained contact, however tenuous, with Rigel during the Reverse and unto modern times. There are many other dozens of worlds in the Alpha Quadrant and the Beta Quadrant that have remains of Orion settlement on them, but with little or no remaining Orion populations.
By treaty stipulation, these worlds are administered formally by their local governmental entities, who are directly responsible to the Orion Colonial Council. The OCC, on Rigel VIII, is responsible directly to the Federation Council. New Orion Colonies (or old ones, resurrected by the Orion Colonial Council) may apply for membership in the Orion Colonial Council, once viable. After a ten year monitoring and evaluation period, the new colony may apply for Federation membership, per the terms of the Treaty of Rigel.