The law exists to protect individual rights and liberties both in substance and in procedure.
Due Process and the Rule of Law are two concepts that have been supported consistently as fundamental principles of the English and American Constitutions. The first is a rule set for establishing and enforcing the law. The latter is a concept by which society is bound and without which society disintegrates.
At face value they both apply to the Government: that governmental power be bound strictly by law in order to protect individual freedom or liberty.
But at the meta level they embrace the entire society:
The entire society requires a means by which individuals receive the fairest possible treatment, both in establishing and enforcing the law. Due Process provides that means by defining steps that must be taken before a law is established and before it is enforced.
Having received the law, the entire society requires a means to ensure that fairness is extended to all members. The Rule of Law provides that assurance by stating that promises given (the law) shall be upheld and broken promises shall be punished.
If Due Process has not been followed in establishing the law the people will find it to be unjust and will refuse to obey it and others will be hard pressed to enforce it. However, if Due Process has been followed and people still refuse to follow the law then others will feel fully justified in enforcing the law as punishment for a broken promise. At that point Due Process returns to ensure that the punishment is applied in, once again, the fairest possible way.
Absent these two principles, the society will disintegrate into chaos.