The mysterious relationship between the foreign investor and the host state has always been described as unbalanced or asymmetrical, since there is a real overprotection of the private party to the point of sacrificing, sometimes, vital interests of the host state of the investment.Far from being pessimistic, like Professor Patrick Juillard who said that: " The conventional system is not balanced, and we do not even see the beginnings of balance on the horizon"We believe that the requirement of conformity of the foreign investment to the law of the host State is a new trend in international investment law and arbitration practice aimed at intensifying the glare of sovereignty and ensuring the reaffirmation of the host State.As a result, a foreign investor who violates the domestic law of the host state risks being deprived of the international protection it seeks. In other words, the domestic legality of the foreign investment is a condition for access to investment arbitration and the benefit of an extremely strong protection system.