In addition to its influence in the courts, Epstein's book eventually had an enormous impact on legal scholarship, as well. Takings is probably the most-cited book about the Takings Clause published in the last fifty years, if not ever. In the most recent edition of the leading introductory property law textbook, Epstein is cited more often than almost any other takings scholar.
Few scholars and judges fully agree with Epstein's position that almost all regulations that restrict property rights should be considered "takings" that require compensation under the Fifth Amendment. But, thanks in considerable part to Epstein, there is now widespread acceptance of the idea that the range of government actions that qualify as takings should be much broader than it was under the prevailing view thirty years ago. For a long time, Epstein was much less successful in persuading the legal community to support a narrower definition of what qualifies as a "public use" justifying the use of eminent domain (a topic to which he devoted a small part of Takings). But, since the Supreme Court's controversial decision in Kelo v. City of New London (2005), mainstream opinion has moved in his direction on this issue, as well. As discussed more fully in my book about Kelo and its aftermath, the debate triggered by the decision has made advocacy of a narrow view of public use intellectually respectable once more.
Epstein's influence is in part the result of the attractiveness of his arguments to libertarians and conservatives. But it is also due to the fact that, by the early 1980s, judicial protection for property rights was so weak that even many moderates (and at least a few liberals) were uncomfortable with some of the results. For example, it seemed perverse to many that, so long as it did not physically "occupy" the land, the government could almost completely wipe out the value of a property owner's rights without paying any compensation whatsoever. Epstein's work gave voice to widespread concerns that, until that point, had largely gone unarticulated (at least not in an analytically sophisticated way). Moreover, as Epstein powerfully explained in his book, the intellectual foundations of the then-dominant view of takings were, at the very least, extremely questionable, and thus ripe for a comprehensive critique.
What was true of takings doctrine thirty years ago may well be true of administrative law today. Hamburger's claim that much of modern administrative law is unconstitutional has obvious appeal to libertarians and conservatives. But you don't have to be a libertarian or conservative to be bothered by the reality that vast swathes of law are made not by Congress, but by unelected bureaucrats, exercising wide-ranging discretion over many aspects of our lives – often with only minimal oversight by elected officials.
As Hamburger explains, this state of affairs seems at odds with the text and original meaning of the Constitution – an objection that has resonance in an era when originalism has attained widespread acceptance among many liberal constitutional theorists, as well as those on the right. Perhaps even more importantly, it is at odds with the notion (at least as popular on the left as on the right) that government should be democratic, and that binding laws must be made by elected officials answerable to the people.
One notable difference between Hamburger and Epstein is that the former is not a libertarian like the latter. Hamburger's political views seem relatively mainstream, as far as I can tell. Unlike Epstein, Hamburger is not an enemy of modern activist government. He just argues that it should be run by laws made by elected legislatures rather than unelected bureaucrats. Hamburger's position might therefore be easier for moderates and liberals to swallow than Epstein's. At least in principle, it is compatible with as wide a scope for federal regulation as exists today (though I am more skeptical than Hamburger that such a large regulatory state can function without massive delegation to bureaucrats).
As with Epstein's theories, I doubt that Hamburger's position will be fully adopted by the mainstream anytime soon. But it is quite possible that mainstream thought will move substantially in his direction, as it did with Epstein. For example, judges and legal scholars might conclude that delegation to agencies should be more tightly constrained than it is now, even if not nearly as much so as Hamburger advocates. As Hamburger himself puts it, the administrative law emperor really is naked, and is therefore ripe for a takedown – much like takings law was thirty years ago. At the very least, I think Hamburger's book – like Epstein's – will ultimately be widely recognized as a major milestone in the debate over the issues it addresses.