InterDep was a global paramilitary organisation formed of Street Judges and Tactical Arms Judges from across the world, introduced and later disposed of in Dave Stone's Virgin Books novels. It was set up after Judgement Day and located on the moon, intended as a harsh response to new global threats. Unknown to most but the highest-ranking Judges, it was the latest in a line of front organisations for a secret global organisation that had evolved out of the Earth's pre-Judge secret intelligence agencies, aiming to keep the world in a stable, static status quo; the Culling Crew was their more covert wing. The Chief Judges were quietly aware of this system and would, at times, use it.
Deathmasques and The Medusa Seed set up the concept, of a multinational group of tactical Judges that enforced international law - i.e. whatever the Justice Departments could agree among themselves was a crime. The first book retconned that the global summit on Judgement Day had been an InterDep conference; the second that there was international InterDep law at work in the "Hinterlands" (i.e. Alientown) sectors around spaceports, rather than internal city law.
Wetworks established the precise nature of InterDep and that it had fifty thousand Judge soldiers on semi-permanent secondment. It had operational autonomy and required a "quinquevirate" (i.e. Council of Five) of political representatives before it would detail its operations. Due to the chaos of both international and domestic politics in the 22nd century, this meant InterDep was free from any real oversight.
The People had become an organisation that existed for the sake of existing and so were swiftly compromised by a group of corporations, who put the psychotic control freak Harvey Glass in charge. They decided to sell Earth's population, with the highest bidder being an alien race who watched it for entertainment purposes and had grown tired of the Judges. To make the planet easier to control and turn into a giant movie set, InterDep soldiers were brainwashed to want to clear out "traitors" in the megacities; InterDep was caught backing a faction in the New Jerusalem civil war and running dirty tricks in Ciudad Barranquilla, while Culling Crews quietly murdered thousands to provoke global anarchy.
An InterDep summit in 2117 to discuss greater involvement in the megacities drew out various high-ranking Judges. Global riots were then triggered, leading to InterDep forces being requested to intervene - a pretext for imposing global martial law and imposing total control. Thanks to Dredd, the InterDep forces were killed before landing, the sight of their ships exploding overhead stalled the global riots, and the organisation shut down. Almost immediately after, the Justice Departments began to consider starting another Culling Crew.