How did the prosperous abbasid dynasty become politically divided

After the death of a prominent Arab ruler, his son's fought and tore the city apart. A lack of qualified arabs meant that they had to employ non-arabs as caliphs and then it became corrupt

Assemblies do not have written codes of laws. laws are matters for magistrates and courts, not assemblies. codes of law are things such as civil law, criminal law, and constitutional law. what assemblies have are procedures regarding debating, voting and other business they might carry out.  also note that rome had three assemblies: the assembly of the soldiers, the assembly of the tribes, and the plebeian councils.