The imperial sentient rights I am aware of in canon are:
- freedom from enslavement
- freedom of access to travel
- trial by jury when off homeworld.
- Ability to appeal local courts to the Noble and/or the subsector moot.
Note that, by not restricting the status, spies are subject to charges of treason, rather than espionage. So that Zhodani or Mandannin spy isn't tried as if a foreign agent -- they're tried as a traitor to the Imperium. It's a pretty slick pro-immigrant status, and it eliminates separated processes for the 6 clades - Tourists, Diplomats, Guest Workers, unnaturalized immigrants, naturalized immigrants, and locals
It also implies a lack of ambassadorial access to diplomatic immunity.