Governments of Men Governed by Laws

Arnold Kling reminds me of this Woodrow Wilson stunner:

I am not repeating the famous sentence of the Massachusetts Bill of Rights, “to the end that this may be a government of laws and not of men.” There never was such a government. Constitute them how you will, governments are always governments of men, and no part of any government is better than the men to whom that part is entrusted. The gauge of excellence is not the law under which officers act, but the conscience and intelligence with which they apply it, if they apply it at all.

I've always been fascinated by this passage because it is both obviously true and obviously false. How it can be both at once?
Wilson is right that laws are not magic spells that bind the rulers to enforce them. The effective law is the law applied by the ruling class. He's right about that. But not so fast. A well-designed constitution knows this and sets competing ruling elites jealous of their turf against each other. The will of some officers of the law can get us a long way in checking the will of others. It's amazing how power-seeking opportunists can become sticklers for the letter of the law. Of course, if they all manage to collude, we're pretty close to Wilson's world, but perhaps not entirely in it. For what determines the attitude of the ruling class to the laws? In a constitutional moral culture, like America's, the Constitution is widely believed to have a bit something more than merely conventional moral authority. Some of the ruling class, including many of the judges in the court of final appeal, will share this belief, and if they don't they'll have to be pretty coy about it in order to avoid political backlash from the constitution-loving people and their very learned and motivated constitutional lawyers. Under those conditions, the laws will tend to guide action, if only loosely. In that case, the content of the laws surely to a large extent determines the excellence of government.
So, sure. Constitutions are rarely constraints on political behavior in the absences of a political culture that buys into the legitimacy of the constitution. But some constitutions, if faithfully applied for enough time, can help create social conditions that lead the people living under the constitution to internalize and affirm its values and principles. When folks like Wilson complain about our antediluvian constitution, they're really complaining about the moral culture that the constitution itself helped to create.
I think if you put it all more plainly, Wilson's point is obviously crazy. Laws change all the time and things get better or worse because the laws do tend to get more or less faithfully enforced and so what the law says matters. If the ruling powers didn't need to actually change the law to get things done, but merely needed to do their thing with “conscience and intelligence,” then the ruling elite would worry less about changing the laws than they actually do.