Defensive-only doctrine

The defensive-only doctrine, also known as the Ascendancy honor code, Chiss codes of conduct, or non-aggression laws, was a law of the Chiss Ascendancy that rendered first strikes in warfare illegal and punishable by exile. Through the influence of the ruling Aristocra and the Chiss Academy, Chiss society considered pre-emptive strikes taboo. The law was in place 1,000 years prior to 22 ABY and was one of the central tenets of Chiss society.

The Chiss Force Commander Mitth'raw'nuruodo, known as Thrawn, violated the law in 27 BBY, when he destroyed the Republic starship Outbound Flight. Thrawn convinced the Ruling Families to allow him to retain his position, although he had still created enemies for himself. After violating the law again in another conflict Thrawn was stripped of his rank and exiled to a planet on the edge of Imperial territory, where he was collected by Voss Parck.

In 22 ABY, the issue on preemptive strikes along with their defensive-only doctrine became a subject of strenuous debate among the Nine Ruling Families.

In 36 ABY, Luke Skywalker considered the possibility that the Chiss Ascendancy had rejected the law in response to changing galactic circumstances, causing the Swarm War with the Killik Colony. Jacen Solo, aware of the Chiss policy on preemptive strikes, attempted to frame the attack of a Chiss supply depot at Thrago on the Killiks, hoping to incite a Chiss counterstrike.