Non bis in idem rule is one of fundamental elements of criminal justice and in other words is basis of principle of observing justice and fairness in procedural Law that its practical representation is more evident in stages of hearing (particularly, in stages of prosecution, trial and punishment). The central core of this rule prevents states from recurrent prosecution and punishment of individuals because of committing a certain crime.In Rome statute, this important principle was noted. This rule was also put in international criminal court statute for former Yugoslavia and Rwanda and it was approved in an emerging phenomenon during history of Law that is during discussion and study for one month in world conference of Rome to establish permanent international criminal court. This rule was recognized as a given principle and a guide for observance of criminal Law. Also, when codifying draft of law of against human security and peace, observance of this rule was considered. This writing tries to define and study application of this important rule in 3 levels; inland, firstrate and second- rate international.
