This chapter and the two that follow turn from the macro-level of the overall constitutional order to the micro-level of particular constitutional rules and principles. The same themes operate at both scales: in the large or in the small, precautionary constitutionalism focuses to excess on targeted political risks while ignoring countervailing risks, collateral harms, and unintended consequences. At either scale, a mature approach to constitutionalism strives for optimal rather than maximal precautions against salient political risks.

In this chapter, I study the political management of impartiality and its various antonyms, especially self-dealing and biased decision making. In constitutional theory, the appeal of impartiality commands widespread consensus; who could be in favor of official self-dealing or bias? Yet I will suggest that as a normative matter, impartiality is a good to be optimized, not maximized; and as a positive matter, U.S. constitutional law surprisingly often abandons the ideal of impartiality in favor of other goods.

The lens through which I will examine impartiality is the legal maxim nemo iudex in sua causa – no man should be judge in his own case, or cause. The nemo iudex principle is widely thought to capture a bedrock principle of natural justice and constitutional democracy. The U.S. Supreme Court calls it “a mainstay of our system of government” and regularly invokes it in diverse contexts, most famously as a principle of natural law in Calder v. Bull and, implicitly, to justify constitutional judicial review in Marbury v. Madison.