New Jerusalem is a megacity and capital of Ethiope: a state encompassing former Ethiopia and most of Somalia. (The Somali territory is disputed.) It is one of the signatories to the Hiroshima Accord and has a nuclear arsenal.
The city and nation are considered the Jewish homeland.
New Jerusalem's predecessor states fought in the Credit Wars.
After the Atomic Wars of 2070, Israel was destroyed. Through unspecified means, New Jerusalem was formed as the centre of a replacement homeland. Ethiope signed up for the Hiroshima Accord.
In 2111, an archaeological expedition found an ancient matter transporter in the Great African Dustbowl that could send mass to a Dyson Sphere. New Jerusalem was at the time in a short-lived trade agreement with Mega-City One and knowledge of the transporter was passed on during a negotiation. When a crisis on the sphere happened in 2116, it was assumed that the initial military response, if any, would come from Mega-City One and New Jerusalem.
During a global psychic disturbance in 2116, religious icons dripped with blood.
A civil war was raging in 2117. The compromised InterDep (out to increase global violence) supported the Christian paramilitaries, concerning the other city-states. "Backstreet torture" was known to have been done.
When the Four Horseman manifested in 2142, Nu-Jerusalem was one of the megacities whose nuclear missiles began to try and fire themselves. 
The specifics of the New Jerusalem/Ethiope Judge force are unknown. What is known is that the Pan-African Judges have no jurisdiction in Ethiope territory. The Pan-African Judges wanted to get InterDep more autonomy even as it was arming anti-judicial forces in New Jerusalem. 
Conception in the comicEdit
A northeast African megacity was first shown in the "Dredd's World" feature in Mega-Special #1: the city was unnamed but drawn as covering Etritrea, part of Ethiopia, coastal Sudan, and Egypt. Two years later, prog 701's world map showed a much smaller city inside Ethiopia (not reaching the coast) and named it New Jerusalem.
The later map for Pan-African Judges would add in the Ethiope concept and establish the areas as a "new Jewish homeland". How post-war Ethiopia & Somalia and a megacity was taken over by ethnic Jews has never been covered.