Galactic Code

The Galactic Code is a non-binding diplomatic agreement, tacitly agreed to by space-faring empires, that forbids the use of superweapons on other empires. The code provides the assurance of fairness for all interactions between empires, to the degree that an empire is not doing permanent damage to the Galaxy. It is based around fair play, and because of this an AI empire will not break the Galactic Code. It resembles the Geneva Convention or the International Space Treaty.

WMDs
Aggressive actions against another race break the Galactic Code when the other race is unable to defend itself, as it is seen as unfair to the peoples of the galaxy. This is similar to the real-life concept of "War Crimes". These weapons include: Rendering a planet uninhabitable does not break Galactic Code; however, if the planet was owned by another empire, it will create a Very high negative Relation Bonus. This includes making a Grox Empire planet habitable for other races; all of their planets are T0, which is required for them to live due to their unique physiology. Raising the T-Score to T1 will kill all of the inhabitants. Static Cling, while temporarily disabling a planet's defenses, does not in and of itself cause the destruction of the race inhabiting the planet and hence does not break the Galactic Code, even if used offensively.
 * Gravitation Wave - Destroys all buildings on a planet, killing all sapient inhabitants, even if they are not in the space stage.
 * Fanatical Frenzy - Instantly takes over a planet, presumably killing all former sapient residents
 * Planet Buster - Destroys the entire planet permanently.

In Civilization stage, you can gain the Gadget Bomb consequence ability by completing Tribal stage aggressively. If you use it against a city, all relationships with other cities will drop by 90 for "Using nuclear weapons", similar to using weapons of mass destruction on a planet in Space stage and getting a significant decrease in relationship for breaking the Galactic Code.

Consequences
Breaking the Galactic Code on a given planet will give a negative Relation bonus to any empires with a radius of 10.00pc around the point of transgression. Breaking the Code can start multiple wars even if the war-declaring empire has lost nothing in what was done; being at war with the empire on which a WMD is used does not excuse its use; and even allies will not ignore the transgression. The maximum negative effect caps out at -200. The Grox, however, admire the breaking of the Galactic Code unless, of course, the transgression is against them. Any use of a WMD on a nearby planet will boost their Relation Bonus with you, up to a maximum of +50.