The effective factors in states contractual liability declination

states are the preservers of public interests in a society. Regarding states’ authorities in administrative contracts, there are special rules governing these type of contracts which are different from rules governing private law contracts. However, beside sovereignty authorities in administrative contracts, states also have responsibilities. The realization requirements, effects and the causes of declining state’s contractual liability, have special rules and principles which are necessary to be studied exactly and it is also necessary to recognize the distinction of rules governing them from the rules governing private law contracts. In this article, by studying related laws and regulations, we are going to recognize the factors leading to decline of states’ contractual liability and to consider the requirements and effects of these factors. The causes of declining states’ contractual liability are termination, nullity, transition, modification and special agreements on increasing, decreasing or declining states’ liability, each of them has special requirements and effects, which will be studied here.