yazzi, i'm sure if you were to study the ancient egyptians' pantheon and their beliefs, it would surely guide you in the right direction. i am not that very knowledged in this area, at least not to tell you the exact ancient egyptian laws of justice, but i do know that every culture, be it ancient or not, has had their own rules and laws since the beginning of time...i believe even cavemen tribes had their own rites of justice. ma'at and amun-ra were two different egyptian deities, ma'at being a goddess of justice and amun-ra being a sun god. they both played a part in the afterlife and in weighing a soul's worth to pass on to heaven and guide that soul to heaven after its judgement.
I hope this answers your question, somewhat. You will have to do some more research if you are looking for further detail. :) Thanks and hope you enjoyed the hub!