Few contemporary policy debates are as fraught as those surrounding the future of the modern surveillance state. In the wake of the 2001 al-Qaeda attacks, and facing ongoing threats from terrorists around the globe, U.S. intelligence agencies have pushed hard against legal constraints on their operations. Their startling reach was revealed in 2013, when former contractor Edward Snowden disclosed the operation of secret information-harvesting programs run by the National Security Agency (NSA). As the scandal broke, President Obama defended the NSA program and summarized the dilemma: “You can't have 100 percent security and also then 100 percent privacy and zero inconvenience.”

The high stakes of modern state surveillance and the difficult balance between security and privacy are the subject of Anthony Gregory's American Surveillance. According to Gregory, a research fellow at the Independent Institute and author of The Power of Habeas Corpus in America: From the King's Prerogative to the War on Terror (2013), current battles over government spying are clouded by misplaced anxieties and misunderstandings—in particular, confusion about the essential function of government surveillance and the complex legal edifice upon which American privacy rights rest. The book is really two books in one. The first is an institutional history of American intelligence operations, from the Revolutionary War to the present moment. The second is a legal history of the Fourth Amendment and the convoluted jurisprudence through which American privacy rights have evolved over two centuries.

In the first half of the book, Gregory's chief aim is to clarify the difference between foreign and domestic spying. This difference is crucial, he insists, because the state has a legitimate interest in gathering information about other nation-states, foreign adversaries, and non–U.S. citizens. Too often, he notes, the security imperatives of foreign surveillance—the work of the Central Intelligence Agency (CIA) and the NSA—are conflated with contentious domestic intelligence-gathering programs conducted by the Federal Bureau of Investigation (FBI) and law enforcement. This conflation is problematic, he argues, because it confuses issues of foreign policy and national security with issues of American privacy. The targets of foreign surveillance, after all, have no constitutionally guaranteed rights under U.S. law. (This is a separate problem, as he points out, noting that the U.S. government can spy on seven billion non–U.S. citizens with impunity.)

In making these distinctions, Gregory largely exonerates foreign intelligence agencies such as the CIA and NSA. This is a lopsided history, to say the least. It glosses over violations of non-American human rights, as abetted by covert U.S. support for repressive regimes or outsourced torture. The real villains in this account are the FBI and an increasingly militarized police force. Gregory's analysis of the Fourth Amendment reinforces this perspective, arguing that the domestic war on drugs—notably its expansion of warrantless searches—has done more to erode U.S. privacy rights than foreign spying. While extolling the prowess of the nation's foreign intelligence agencies, and pinning their failures on inept policymakers, Gregory minimizes their domestic threat.

The first half of the book seeks to show how U.S. foreign and domestic intelligence programs have diverged over time—thus shielding Americans from abuses at home—but the end point throws this narrative arc into doubt. As the Snowden leaks revealed, the NSA, an outward-facing intelligence organization, was not just eavesdropping on foreign communications. It was siphoning off huge troves of phone and Internet data, including data belonging to millions of American citizens, all with the flimsiest of legal cover. Gregory is not particularly troubled by this. He suggests that the NSA's surveillance was “mostly safe” and that initial investigative reporting might have overblown the extent of the NSA's domestic spying (p. 120).

Ultimately, Gregory argues that one cannot criticize foreign surveillance programs without questioning the very legitimacy of state power itself. This is the uncomfortable truth that all sides of the debate must confront, as he insists and President Obama's own remarks on the matter echo. The problem, of course, is that security threats rarely sort themselves into such neat divisions. When foreign enemies have domestic sympathizers—Tories, Communists, or ISIS-inspired jihadists—then outward-facing surveillance turns inward. If Gregory's effort to draw hard distinctions between foreign and domestic surveillance is unconvincing, it is because the two are so often interconnected, as his historical survey repeatedly demonstrates.

The motivation behind such forced dichotomies becomes clear in the book's second half. By cordoning off foreign surveillance and issues of state security, Gregory seeks to isolate privacy debates in their domestic context, where the citizen-subjects of government surveillance have constitutional protections and where such debates are actually adjudicated. Here the book has the most to offer. Gregory's analysis of Fourth Amendment protections against search and seizure helpfully contextualizes the development of the modern privacy concept. He highlights the main interpretative conflicts, drawing attention to the attenuation of early property-rights perspectives in light of new electronic media and surveillance technologies. Remote wiretapping and metadata collection confound Fourth Amendment law because, as he shows, “searches” need not involve physical trespass and it is not clear when the information detritus of modern life meets a “reasonable expectation” threshold for privacy.

Given the realities of national security and the affordances of modern communication technology, Gregory is resigned to the inevitability of a powerful surveillance state. After guiding the reader through a thicket of American jurisprudence, he concludes that law alone cannot solve society's privacy dilemmas. “The predicament posed by the NSA, modern police power, and the modern administrative state's multitude of intrusions into private life is not, ultimately, a legal problem. It is a cultural problem, posed to civilization itself” (p. 165). It is worth noting, however, that legal systems do not exist outside of culture. Nor do intelligence agencies.

Though Gregory laments the NSA's having been tarred with the brush of domestic spying, the scandal reminds us that cultural values, enshrined in law and institutional protocols, do not guarantee protection against the state's insatiable need to know. The recent election of President Trump casts the book in a much darker light. Published just as the 2016 presidential campaign shifted into high gear, Gregory’s account ends before FBI director James Comey embroiled the agency in controversy over Hillary Clinton’s email and before allegations of Russian election meddling raised questions about the U.S. intelligence community’s credibility. These events have transformed long-running battles over the state’s right to know into more troubling battles over truth itself. If privacy rights were severely tested by post-9/11 security programs, their fate in a deeply politicized, post-fact world seems even more tenuous.