The Orion Emigration Act, also called the Orion Registry Act, was a treaty signed on stardate 1/9808.15 (c. 2250s) by Botchok Planetary Congress President Vloun and Commissioner Dzwonkowski of the Federation's Rigel Demilitarized Zone Commission.
Following the formation of the Orion Neutrality Area, the Federation had annexed a number of Orion Colonies. The Emigration Act required the registration of all Orions within the newly defined Federation space. Later in the 23rd century, as anti-Orion attitudes in the Federation waned, the Federation Council relaxed some of the restrictions on Orion immigration.
By the terms of the Registry Act, Starfleet had no authority to detain a starship transporting Orions, provided that it had all the correct paperwork and licensing, and most captains did not even attempt to stop them. However, such starships transporting supposedly free Orions were in fact transporting slaves by Orion custom. (FASA RPG module: The Orions: Book of Common Knowledge)