40. So also, the difficulty is not insuperable as regards the other point, namely, that international enactments when once in existence cannot be repealed or amended save by a unanimous resolution of the participant states. Here, too, the analogy between municipal and international legislation must not be pushed too far. Municipal legislation can at any time be annulled or altered by the sovereign law-maker; but international legislation, for want of a sovereign over sovereign states, is not open to such treatment. Here there is a way out, which was in fact adopted at the second Peace Conference, and also at the Naval Conference of London, namely, the enactment of laws so limited in duration to a period of years, that at the expiry of the period every participant state can withdraw. In this way, for example, it was agreed that the law about the International Prize Court and the Declaration of London should only be in force for twelve years, and that any of the powers which were parties thereto might withdraw twelve months before the expiry of that period, and that, if and as far as no withdrawal ensued, these laws should from time to time be continued in force automatically for a further period of six years. This kind of international legislation, with its time limit and the right of denunciation, is to be recommended wherever more or less hazardous legislative experiments are being made, or where interests are at stake which in course of time are liable to such an alteration as obliges states to insist on the amendment or repeal of the previously made law. For example, the International Prize Court as a whole, and its composition, constitution, and procedure in particular, form an unparalleled experiment. But the fact that its institution is only to be agreed on for a period of twelve years facilitates its general acceptance, because of the possibility of either abrogating it altogether, or of reforming it, should experience show this to be necessary. [Sidenote: International legislation no longer to be left to mere chance.]