Debates over government transparency are usually framed as a contest between the executive branch and the rest of us. Transparency is supposed to help Congress, the courts and the public hold the president accountable.

But history suggests that transparency is important for another reason: it helps the president himself keep control over his subordinates.

In a 1975 Senate hearing, National Security Agency director Lew Allen admitted that the NSA "had never received the explicit approval of incumbent presidents or attorneys general" for its program of secretly reading Americans' international telegrams.

In another Senate hearing that same year, a White House aide who had planned a controversial domestic surveillance plan in the Nixon administration, testified that the White House "didn't know half the things" intelligence agencies were doing that might be legally dubious.

"If you have got a program going and you are perfectly happy with its results, why take the risk that it might be turned off if the president of the United States decides he does not want to do it," he asked. He also said that "interagency jealousies and rivalries" caused to agencies conceal the extent of their domestic surveillance activities. Agencies didn't want to alert their bureaucratic rivals that they were encroaching on their turf.

Secrecy also makes it easier for executive branch officials to cut legal corners on otherwise legal programs. For example, the Patriot Act gave the Bush administration broad authority to issue National Security Letters, secret requests for information that don't require judicial oversight. But a 2007 Inspector General's report found more than 700 cases where FBI agents who didn't have the authority to issue NSLs had improperly obtained information by telling companies that "exigent circumstances" required that the information be turned over immediately, without even the minimal checks required by the NSL rules.

In all of these cases, secrecy made lawbreaking more likely. If an NSA or FBI employee suspected the law was being broken, there was no easy way to blow the whistle. And with limited oversight, it was less likely that Congress or the courts to notice something was amiss. So the abuses festered for years.

So far, the controversial surveillance programs revealed by Ed Snowden's leaks appear to have been conducted with the explicit approval of President Obama. And maybe that's because today's executive branch officials have a healthier regard for the rule of law than they had under presidents Kennedy, Johnson, Nixon and George W. Bush.

But it's also possible that the NSA, FBI, and other agencies are engaged in lawbreaking that neither the Congress nor the president know about yet. Some abuses festered for two decades before being brought to light by Congressional investigations in the 1970s. We haven't had a comparable investigation of intelligence abuses under the last six presidents. And today's executive branch is even more obsessed with secrecy than it was during the Cold War.

More transparency and oversight wouldn't just make it easier for the public to trust their government. It would also make it easier for President Obama himself to keep his own subordinates in line. By insisting on widespread secrecy and aggressively prosecuting whistleblowers, President Obama has cut himself off from valuable sources of information about what his subordinates are doing. More transparency and oversight would allow the press, the Congress, and the courts to act as the president's eyes and ears, alerting him to cases where his subordinates have gone beyond what the law allows.