There are 10 unique codex entries in the Game Rules section on the Republic Fleet. 1 is accessible to all players regardless of class or faction and 9 are unobtainable.
Advanced Class: Commando is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Trooper
Associated Achievement: None
Advanced Class: Gunslinger is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Smuggler
Associated Achievement: None
Advanced Class: Jedi Guardian is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Jedi Knight
Associated Achievement: None
Advanced Class: Jedi Sage is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Jedi Consular
Associated Achievement: None
Advanced Class: Jedi Sentinel is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Jedi Knight
Associated Achievement: None
Advanced Class: Jedi Shadow is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Jedi Consular
Associated Achievement: None
Advanced Class: Scoundrel is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Smuggler
Associated Achievement: None
Advanced Class: Vanguard is unobtainable.
Codex type: Game Rules | Faction: Republic | Class: Trooper
Associated Achievement: None
Galactic Strongholds is obtained from interacting with a Clickable Plaque.
Codex type: Game Rules | Faction: Both | Class: All
Associated Achievement: None
Social Points is unobtainable.
Codex type: Game Rules | Faction: Both | Class: All
Associated Achievement: None