Ackerman's remarks about a Kantian approach to the taking question occur in Chapter 4 of his 1977 book, Private Property and the Constitution. In Ackerman's terminology, the term "Kantian" covers everyone who rejects utilitarianism on the ground that "individuals have certain rights simply because they are autonomous beings worthy of respect -- rights which cannot be overridden simply by an appeal to general Utility." Ackerman treats Kant as "a symbol of [the] principle . . . that Policymakers are not to conceive of their fellow citizens as merely means to the larger end of maximizing social utility, but are instead to treat them as ends in themselves."

Ackerman's discussion of a Kantian approach to the taking question does not aim to provide a fully refined and developed Kantian analysis of takings, nor was Ackerman trying to figure out what the historical figure named Immanuel Kant would have said about the question. It would be well to recall here my summary above of his book's main themes. Given those main themes, Ackerman wanted to show that sharply contrasting results at the level of legal doctrine and decision might arise within the confines of what he called "scientific" adjudication, as well as between scientific and "ordinary" adjudication. Accordingly, he included broad-brush discussions of "utilitarian" and "Kantian" approaches to takings to show how a clash of moral theories at a general philosophical level could play out in disagreement about particular legal doctrines and decisions.

Back, now, to our hypothetical rent law. Suppose a good estimate of the key quantities for that law is that the total net social benefits are greatly in excess of the demoralization costs if no compensation is paid, but are only slightly in excess of the settlement costs involved in calculating, negotiating, adjudicating, and administering payment of compensation to every adversely affected owner of rental housing. In that case, the utilitarian judge is supposed to enforce the law and deny compensation.

Ackerman's Kantian is forced to object. From her standpoint, the utilitarian judge is making the owners "sacrific[e] some of their rights simply because others would find it terribly convenient for them to do so;" and, Ackerman asks, if that is not a case of making someone serve as "a means for the satisfaction of another's ends," what would be? It is obvious, Ackerman says, that the only way to avoid a violation of the Kantian injunction -- never treat a person as merely a means to another's ends -- is to compensate all affected owners to the point where everyone is in at least as good a position as they would have been in without the rent law. The fact that doing so defeats the social goal of maximizing the over-all net sum of benefits from the rent law, by forcing society to bear settlement costs that exceed the demoralization costs that otherwise would have resulted, cuts no ice with Kantians.

From here on, Ackerman's discussion gets into a few refinements that you can discover by looking at his book. But you do not need them in order to grasp his main point: Utilitarian scientific adjudicators and Kantian scientific adjudicators will part company in a major way over how to decide whether a government regulation of property amounts to a compensable taking. 

Recall that the Kantian and utilitarian approaches are opposed along the two distinct and cross-cutting axes of consequentialist/non-consequentialist and right-based/goal-based. (Remember the Table.) Can you specify which of those two lines of opposition between the two approaches is responsible for the doctrinal dispute between them that Ackerman describes?