The German Reichstag building is pictured through a flag depicting Edward Snowden. (Tobias Schwarz/Reuters)

In 1970, Christopher Pyle disclosed in public writing that the U.S. Army was running a domestic intelligence program aimed at anti-war and civil-rights activists. His disclosure began a series of public-accountability leaks, the most famous of which was Daniel Ellsberg's leak of the Pentagon Papers. These disclosures, the FBI's notorious abuses in COINTELPRO, and the Watergate leaks taught Americans that the national-security system can take profoundly dangerous constitutional turns. They formed the foundation of the political will that led to the passage of the Foreign Intelligence Surveillance Act in 1978. And although Ellsberg and his collaborator Anthony Russo were prosecuted, their cases were dismissed.

This series of events that helped cement the role of unauthorized public disclosure as a systemic check on the predictable cycles of error in the national-security system. The leakers of the 1970s became heroes who exposed systemic failure, and the nation did not punish those who helped it correct the excesses.

For a quarter of a century, leaks continued apace, though not the kind of public-accountability disclosures that typified the early 1970s. These were the normal grist for the mill for the national press: gossip and backstabbing, trial balloons and glorified insider war stories—leaks that, as David Pozen showed, existed long before the 1970s and have continued without noticeable increase or decrease ever since. Only one leak, the clearly improper disclosure of satellite images of a Soviet aircraft carrier to Jane's, was ever prosecuted, and the norm of not prosecuting for leaks to the press was so strong that Senator Daniel Patrick Moynihan persuaded President Bill Clinton to pardon that one offender.

It was only in 2002, when Jesselyn Radack disclosed that the prosecution of “American Taliban” John Walker Lindh had involved several violations of Lindh's constitutional rights, that the new wave of whistleblowing and public-accountability leaks reemerged. Thomas Tamm and Russ Tice each disclosed the Bush administration's warrantless-wiretap program to The New York Times; AT&T employee Mark Klein disclosed the company’s complicity in illegal wiretapping; and William Binney, Thomas Drake, and others challenged internally—and in Drake's case disclosed publicly—early aspects of NSA dragnet surveillance. Chelsea Manning disclosed a major document cache to WikiLeaks, driven by what she viewed as American forces’ callous disregard for civilian casualties and silent complicity in Iraqi government torture. Most critically, Edward Snowden's disclosures led to the introduction of dozens of bills in Congress, a judicial opinion, and two executive-branch independent reviews that demanded extensive reforms to surveillance programs.

As with the Vietnam-era leaks, the wave of accountability leaks in the past dozen years was the result of the national-security establishment overstepping its constitutional boundaries in a state of emergency. Reacting to the shock of 9/11, the national-security system responded as best it could. Some of the responses were measured and necessary. Others were abusive mistakes followed by aggressive cover-ups. The army ordered an inquiry into allegations of torture by military personnel, then forced out the general who dutifully reported the "sadistic, blatant and wanton" "systematic and illegal abuse" he found. The CIA embraced torture with a vengeance, lied about it to the administration and Congress, and went so far as to spy on its Senate overseers in its attempt to cover its tracks. The NSA built a surveillance apparatus that overstepped its statutory and constitutional authority, and in the process of normalizing that apparatus dragooned parts of the judiciary and Congress into providing a veneer of legitimacy to its actions. Viewed in this light, the war that President Obama and his attorney general have waged on whistleblowers can no longer be reasonably seen as simply a response to increased leaks in general. Instead, it reflects an increasingly embattled national-security system pushing deeper into barely defensible or indefensible constitutional dead ends and ramping up aggressive criminal prosecutions to defend itself from the ultimate failsafe for stopping abusive systems: individual conscience.

One thing is clear. Without the men and women of conscience who have come out over the past 12 years and disclosed aspects of the abuses, the system would have kept on grinding.

The single most important lesson of Snowden's disclosures is that even well-designed and well-intentioned systems of checks and balances become corroded and subverted over time. No matter how perfect a set of rules or an institutional or organizational system was when it was created, it cannot remain so in the face of time, change, and the pressures of new emergencies. The FISA system that emerged from the 1970s worked reasonably well in the latter stages of the Cold War, when it was grappling with the kinds of threats and the technological environment for which it was designed. But as Binney put it, everything changed after 9/11. The urgency of preventing another attack swept away the rules. Partly in response to heroic efforts of some insiders to change policies, and mostly due to the public exposure of the warrantless wiretapping program, elements of the judicial-oversight system were reintroduced starting in 2006, and Congress passed the FISA Amendments Act in 2008. But the practices that had developed had become so complex and diverse that the new oversight system was completely inadequate to contain them.

The failures of the FISA system, both old and new, are not unique. All large systems suffer from these kinds of failures as they age, as new conditions challenge old practices, and as the rationale for processes once cherished is lost in the humdrum of bureaucratic routine. Democrats might prefer to focus on General Motors or Lehman Brothers. Republicans will emphasize the Obamacare website or the Department of Health and Human Services. And almost everyone points to the FEMA Katrina response. Unless one believes that the national-security system has a magical exemption from the dynamics that plague any of these other large organizations, one should expect large and substantial mistakes from the complex interaction between the Department of Defense, the CIA, NSA, and FBI and their various contractors, from Boeing and Lockheed Martin to Halliburton and Booz Allen Hamilton.

Whistleblowing is a central pillar of the way American law deals with these dynamics of error, incompetence, and malfeasance in large organizations. From workplace-safety violations to Medicare and Medicaid fraud to anti-corruption campaigns around the world, we protect and reward those who follow both internal procedures and those who expose abuse to the public. Internal audit and review processes, while important, need the backstop of insiders with knowledge.