Can you retreat a unit that was played by Aurora's ability?

Ruling: You can only retreat a friendly unit, so you cannot retreat an opponent's unit played by Aurora.

Sequence:

• Aurora's trigger plays the unit on resolution
• You cannot react to permanents being played
• You cannot react to Aurora's trigger to interact with the unit it plays
• However, you can react to any "When I'm played" triggers from the unit Aurora played

Nuances:

• If Aurora plays a unit with an on-play trigger that has less than 3 might, you could use cards like Gust to interact with it in response to that trigger