The issue is of particular relevance in an economic context in which economic, technological, or internal resources are insufficient for the realization of major development projects, so it must be foreign investors who provide those resources and contracted with the State, by submitting at the same time to its jurisdiction. No wonder, then, that, through the last decades, international economic law has been dealing with developing new concepts and institutions whose purpose is to provide legal certainty to those contractual relationships in which the State itself considers justifiable to delete the greatest non-commercial risk resulting from their particular situation how contracting. Some of these concepts and institutions are confined to relations legal between States and nationals of other States, as in the case of international treaties relating to the protection of foreign investments. On the other hand, there are other concepts and institutions that have been developed in the domestic law of each country, in order to avoid legislative authority for State or jurisdiction over the co-contratante part, represent a deterrent for the conclusion of a contract considered of national interest or an additional factor of non-commercial risk that such co-contratante must be regarded in its economic model at the time of negotiating the terms and conditions of the contract. The need to provide legal certainty to the relationships of individuals with the State, when it acts in use of its powers of imperium, is the raison d ‘ etre of the contracts law. The contract law then meets the purpose of providing legal certainty to investors in two different ways: through the stabilization of the legal framework applicable to the legal relationship wealth created by the contract and through the modification of the legal framework applicable to a contract with the State of administrative law to civil law. Is not in discussion the fact that the State can dissociate or not his impremium powers, which by the way are inherent. .