Law and political wisdom may or may not be on the same side.
If they are not, the insistence upon the letter of the law will be in-
expedient and may be immoral. The defense of the limited interest protected by the particular rule of law will injure the larger good which the legal system as a whole is supposed to serve. Therefore, when basic issues, on the national scene, in the form of economic, social, or constitutional conflicts demand a solution, we do not as a rule appeal to the legal acumen of the judge but to the political wisdom of the legislator and of the chief executive. Here we know that peace and order do not depend primarily upon the victory of the law with the aid of the sheriff and of the police but upon that approximation to justice which true statecraft discovers in, and imposes upon, the clash of hostile interests. If sometimes in our domestic affairs we are oblivious to this basic truth of statesmanship, we pay with social unrest, lawlessness, civil war, and revolution.
On the international scene we have not stopped paying for our forgetfulness since 1914, and we seem to be resolved to pay with all we have for the privilege of continuing to disregard the lessons of history. For here our first appeal is always to the law and to the lawyer, and since the questions which the law and the lawyer can answer are largely irrelevant to the fundamental issues upon which the peace and welfare of nations depend, our last appeal is always to the soldier. Fiat justitia, pereat mundus becomes the motto of a decadent legalistic statecraft. But this alternative to our legalism we do not dare face as long as we still can choose. Thus, an age which seems to be unable to meet the intellectual and moral challenge of true statesmanship, or to face in time the cruel alternative to its political failure, takes refuge in the illusion of a new diplomacy. The old diplomacy has failed, it is true, but so has the new one. The new diplomacy has failed and was bound to fail, for its legalistic tools have no access to the political problems to be solved. The old diplomacy has failed because the men who used it had forgotten the rules by which it operates. Blending misplaced idealism with misunderstood power politics, our statesmen vacillate between the old and the new, and each failure calls forth an ever stronger dose of an illusory remedy. Whether they swear by Wilson or follow Machiavelli, they are always Utopians pursuing either nothing but power or nothing but justice, yet never pausing to search for the rules of the political art which, in foreign affairs, is but another name for the traditional methods of diplomacy well understood.
Hans J Morgenthau, ‚Diplomacy‘ (1946) 55 Yale Law Journal 1067, 1080