Official rule text
13 COMBAT AND UNIT ABILITIES ✦During a combat roll or a roll for a unit ability where a player and their ally each have units present, both can participate in the same roll; their rolls are combined and hits are assigned as normal. When an opposing force produces hits against allied players, the allies will decide together which units the hits will be assigned against; if they cannot come to a consensus, the active player assigns the hits. ✦Effects that produce hits that are assigned by an opponent against an allied pair can be assigned to either ally’s units in any combination. ABILITIES AND EFFECTS ✦Your ally’s units count as neither your units nor as other players’ units for the purpose of resolving game effects and abilities. ✦Abilities that trigger when a player activates a system that contains another player’s units, planets, or command tokens do not trigger when those players are allies. ✦Your unit abilities (space cannon, planetary shield, etc.) do not affect your ally. ✦Agent abilities can be used on your ally. ✦Your ally’s planets count as your planets for the purpose of resolving abilities, but you cannot exhaust them and they do not count for scoring objectives or scoring the “Imperial” victory point. ELIMINATION ✦A player cannot be eliminated as long as their ally controls a planet.