A reservation to treaty, which purports to exclude or modify the legal effect of certain provisions of a treaty or of the treaty in the application to the State or to the international organization which formulates the reservation, usually results in valid one or invalid one. Among these, there is no special issue resulted from a valid reservation in relation to the formation of treaty. In case of an invalid reservation, however, it is necessary for a few problems to be discussed in order to searching for the reasonable method to develop treaty regime. The problems are as follows; what is the legal effect of an invalid reservation itself? and what are the consequences of that invalid reservation?A reservation that does not meet the conditions of formal validity and permissibility is null and void, and therefore devoid of legal effect. One aspect of the normal consequence of the impermissibility of a reservation is that its author does not have the benefit of the reservation. A reservation is or is not valid, irrespective of the individual positions taken by State or international organizations in this connection and, accordingly, its nullity is not a subjective question or a relative matter. The purpose of the phrase “null and void” in the ‘ILC Draft Guidelines on Reservations to treaties’ is to recall that this nullity is not dependent on the reactions of other contracting States. There are largely two possible consequences for reservations held to be invalid. First, the incompatible reservation may be said to invalidate the state’s instrument of ratification, so that the state is excluded from the treaty as a whole. Second, an incompatible reservation may be severed from the state’s instrument of ratification, leaving it as a party to the treaty without the benefit of its reservation. Considering on the principle that underlies treaty law, which is the principle of consent, the deciding factor is still clearly the intention and will of the State that is the author of the invalid reservation. Entry into force is no longer simply an automatic consequence of the nullity of a reservation, but rather a presumption. It, however, should be borne in mind that the author of the reservation wished to become a contracting party to the treaty in question. It is certainly wiser to presume that the author of the reservation is part of the circle of contracting States or contracting organizations in order to resolve the problems associated with the nullity of its reservation in the context of this privileged circle. Especially, in regard of human rights treaties, it should be encouraged to continue their current practice of entering into a dialogue with reserving States, with a view to effecting such changes in the incompatible reservations as to make it compatible with the treaty.