Citadel Conventions

The Citadel Conventions were a set of diplomatic accords negotiated in the wake of the Krogan Rebellions, drawn up as a response to the devastation of that conflict and as an attempt to distance the Citadel Council from the brutal warfare the krogan had waged. Their central purpose was to regulate the use of weapons of mass destruction across Citadel space, and they also defined the terms by which lesser powers participated in galactic governance, binding every species granted an embassy as an associate member subject to the accords. (Mass Effect)

Origins and scope#

The Conventions emerged from diplomatic talks held after the Krogan Rebellions, both as a reaction to the destruction of that war and as a deliberate effort by the Council to set itself apart from the krogan's methods. Their core function was to regulate weapons of mass destruction, which the accords defined not by raw explosive power but by lasting effect: a weapon that caused environmental alteration to a world. A bomb that merely left a large crater was not considered a weapon of mass destruction, whereas one capable of triggering a nuclear winter was. (Mass Effect)

The rules turned on the value of habitable worlds. The use of such weapons was forbidden on garden worlds, those with ecospheres able to readily support a population, on the principle that a destroyed habitable world would not be replaced for millions of years. The Conventions did not, however, forbid their use on hostile worlds or within sealed space-station environments, and in practice many militaries continued to develop and maintain stockpiles regardless. (Mass Effect)

The tiers of concern#

The Conventions graded weapons of mass destruction into four tiers, with Tier I representing the greatest threat to galactic peace. Tier I covered large kinetic impactors, such as dropped asteroids or de-orbited space stations. These were effectively free and available in any system, since planetary accretion left abundant debris behind, which made them the weapon of choice for terrorists and minor powers. (Mass Effect)

Tier II covered uncontrolled self-replicating weapons, including hostile nanotechnology, engineered viral or bacteriological organisms, self-copying Von Neumann devices, and destructive computer viruses, threats that could lie dormant for millennia before a careless visitor carried them to a new world. Tier III covered large energy-burst weapons such as nuclear or antimatter warheads. Tier IV covered alien species deliberately introduced to crowd out the native forms an ecosystem depended on, a slow form of ecological tampering that could take years to bear fruit and was correspondingly difficult to prove. (Mass Effect)