The biggest connection one can draw between Divine Justice and the human legal system is that the relationship between the people and the governing body is much the same. The citizens and the state (or God) enter into a mutually agreed upon contract (or covenant), by which the one body consents to be ruled by the other, with some conditions. Among these conditions are laws (or God's will). Those who adhere to the laws are considered good citizens; those who violate those laws are subject to punishment. Thus, one may view God's will as law; those who learn to conform to it become the blessed, worthy of Heaven.
A blessed soul cannot maintain his individuality in Heaven because he has willingly aligned his free will with God's.
A blessed soul can indeed maintain his individuality in Heaven because even though he has aligned his free will with God's, God smiles upon and celebrates human diversity.