Who Owns the Sky? is a comprehensive and wonderfully readable account of how the invention of the airplane changed one of the most fundamental premises of Anglo-American property law. The premise is the maxim “cujus est solum ejus est usque ad coelum”—“he who owns the soil owns up to the sky” (6). At the dawn of the twentieth century, the cujus maxim was “a firmly established legal principle” (23) recited in most treatises on property law and enforced in a wide range of cases. By mid-century, the landowner's rights had been substantially reduced, extending only to “as much of the space above the ground as he [could] occupy or use in connection with the land” (253).

Given the maxim's fame, this is quite the tale. Stuart Banner tells it both engagingly and encyclopedically. The scope of his research is extraordinary. As background, Banner traces the history of the cujus maxim through the early Roman, civil, and common laws, and discusses its nineteenth-century application to landowners whose buildings and trees leaned over their property's border; hunters who shot bullets over land they did not own; and farmers whose horses kicked through boundary-fences to injure their neighbors' animals. He covers the initial debates raised by the invention of hot-air balloons in the late eighteenth century and by airplanes in the early twentieth century. He also recounts the impact of manned flight on the rights of sovereignty before and during World War I.

Having raised the conflict between the cujus maxim and the airplane, Banner turns to attempts to resolve it through common-law adjudication, state legislative cooperation in the enactment of uniform laws, international treaty, and federal regulation. Banner recounts the successes and failures of each approach, showing, for example, how the proponents of federal regulation contended with doubts about the national government's power to reach flights that were wholly within a single state. Through all these approaches, Banner shows the tenacity of the cujus maxim. “Forty years after the dawn of flight,” he writes, “the law of aerial trespass was still partially uncertain. Planes could fly at high altitudes, but whether they were trespassing at low altitudes was still up in the air” (202).

Then came United States v. Causby (1946), in which the Supreme Court “unexpectedly” gave “aviation lawyers” the “uniform nationwide rule” they “had been trying for years to obtain” (256). Causby was not the outcome of an orchestrated litigation campaign brought by the affected industry or an issue-oriented legal foundation. The aviation industry did campaign for a uniform law, but it “directed [its] efforts at state legislatures … and at Congress” (256). Causby was brought by a country lawyer on behalf of a poor farm family. According to Banner, resting the case on a remnant of the cujus maxim was entirely the work of Justice Douglas, the opinion's “idiosyncratic” author (226). The other Justices did not want to address the “question of an abstract right to the sky,” (249) but “did not care enough about the issue to try to talk [Douglas] out of it” (258).

With the question of ownership of the sky settled, Banner ends his book with an extended coda on changes in the law of national sovereignty regarding airspace and outer space as the age of flight evolved into the age of rockets, satellites, and manned spacecraft.

As a narrative history of the impact of airplanes on the cujus maxim, Banner's book is a complete success. Although it is remarkably detailed, it is written with such clear prose and good humor that my interest never flagged. Even Banner's departures from his focus on the decline of the cujus maxim, for example, his extended discussion of the history of law school courses and academic institutes on air law, are welcome additions to his cornucopia of information.

But Banner has greater ambitions for his book and with them he is less successful. Banner pitches his book as not “just a collection of nutty anecdotes” (2). It is “an intellectual history” of twentieth-century U.S. law and “an extended case study of the relationship between technological change and legal change” (2–3). The intellectual history, however, is a standard rendition of the transition from natural law and legal formalism to positivism and legal realism. Banner explains the relationship between technological and legal change through a conventional law-and-economics analysis of transaction costs. Banner's excursions into theoretical understanding push no boundaries.

Who Owns the Sky? was written with the general public and the inquisitive student in mind. Professors may cull interesting stories from it to enliven classroom discussion and show that property and aviation law can be interesting. It is a trove of stories in which theorists may yet discern additional aspects of the way history, society, law, and technology interrelate.