A while back, one of my colleagues at the University of Michigan complained about not having much power. I countered that he had plenty of power: in particular, he had the power to mint A's, a power that would be quite impressive to his students. What he was complaining about was a feature of any well-run society: he did not have the power to be judge in his own case. He did not have authority to grant himself a promotion, determine his own salary, or give himself a grant—power at least a part of himself sorely wanted. Instead he had the burdensome power and responsibility to be the judge in his students' cases.  

The principle that no one should be judge in their own case was well enunciated more than 2050 years ago in Publilius Syrus's Latin maxim above. The principle that no one should be judge in their own case is then emphasized by John Locke in section 13 of his 2d Treatise on Government: On Civil Government:

To this strange doctrine, viz. That in the state of nature every one has the executive power of the law of nature, I doubt not but it will be objected, that it is unreasonable for men to be judges in their own cases, that self-love will make men partial to themselves and their friends: and on the other side, that ill-nature, passion and revenge will carry them too far in punishing others; and hence nothing but confusion and disorder will follow; and that therefore God hath certainly appointed government to restrain the partiality and violence of men. I easily grant, that civil government is the proper remedy for the inconveniences of the state of nature, which must certainly be great, where men may be judges in their own case, since it is easy to be imagined, that he who was so unjust as to do his brother an injury, will scarce be so just as to condemn himself for it; but I shall desire those who make this objection, to remember, that absolute monarchs are but men; and if government is to be the remedy of those evils, which necessarily follow from men’s being judges in their own cases, and the state of nature is therefore not to be endured, I desire to know what kind of government that is, and how much better it is than the state of nature, where one man, commanding a multitude, has the liberty to be judge in his own case, and may do to all his subjects whatever he pleases, without the least liberty to any one to question or control those who execute his pleasure? and in whatsoever he doth, whether led by reason, mistake or passion, must be submitted to? much better it is in the state of nature, wherein men are not bound to submit to the unjust will of another: and if he that judges, judges amiss in his own, or any other case, he is answerable for it to the rest of mankind.

In other words, with a bit of hyperbole, John Locke says that if we are going to let anyone be judge in his or her own case, we might as well go back to the state of nature. 

One key place where the United States of America violates the principle that no one should be judge in their own case is having many administrative agency decisions (a) decided by agency officials, (b) sometimes reviewed by judges chosen by and paid by that agency and then (c) being reviewed by outside, more independent judges under what has come to be called the "Chevron doctrine," which insists that judges defer to an agency decision if there is any conceivable construction of the law that could justify that agency decision. (See "Jonathan Adler on Neil Gorsuch and Reconsidering the Degree of Judicial Deference to Government Agency Decisions" and the Wikipedia article "Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc." These two references are connected in an intriguing way: Supreme Court nominee Neil Gorsuch, who has eloquently questioned the Chevron doctrine, is the son of Anne McGill Gorsuch (Burford), who was the head of the EPA when its decided to focus on the amount of pollution from an entire industrial plant, rather than from each separate piece of equipment within a plant—the decision that was upheld by the Supreme Court back then.)

To the extent that the Chevron doctrine means in practice that almost all agency decisions are unreviewable, the doctrine effectively allows these agencies to be judges in their own cases. In such a situation, there not be quite as much of a self-interest bias as if one were deciding one's own salary, but enough decisions are made out of power-hunger, anger and extreme ideological interest that some mechanism of review is essential. 

One of the practical difficulties with judicial review of agency decisions is that the agencies tend to have much greater expertise in the relevant areas than a judge typically does. If the Chevron doctrine is modified to allow more judicial review, it is crucial to give judges the intellectual resources they need to understand the issues involved in an agency decision. One approach that many countries follow to a greater or lesser degree is to have judges specialize in certain kinds of cases. That can help. But in the really important cases, more is needed.

I would like to see legislation passed that allows a judge reviewing an important agency decision to convene an expert panel. With the judge as moderator and the one to lead the final decision, the experts on the panel would freely discuss all of the relevant issues surrounding the agency decision. The expert panel, led by the judge, would function as a jury, conducting some parts of the proceedings with the litigants present and some parts of the proceedings without the litigants present.

There are several possible ways to work out the details of how expert panels would work. The basic principle is ensuring that review of the agency's decision is conducted with enough intellectual firepower that there is no presumption that the expert panel's decision is any less informed than the agency's original decision. With a system like this that allows judges of important agency decisions to convene expert panels, there would be no excuse for letting agencies be judges in their own cases to the extent that the current Chevron doctrine allows.