When John Brennan assured the country that the CIA hadn't improperly monitored the Senate team that compiled a report on Bush-era torture, he fed us false information. That much is clear from Thursday's news that "the C.I.A. secretly monitored a congressional committee charged with supervising its activities." Either the CIA director was lying or he was unaware of grave missteps at the agency he leads. There are already calls for his resignation or firing from Senator Mark Udall, Trevor Timm, Dan Froomkin, and Andrew Sullivan, plus a New York Times editorial airing his ouster as a possibility.

President Obama could surprise the country by axing his former counterterrorism adviser, explaining that under Brennan's management, employees broke laws and undermined the separation of powers core to our democracy. Obama may well make a good-faith effort to act in the national interest. But it's impossible to believe that he won't be aware of the following: No U.S. official knows more than Brennan about Obama's many drone killings. Some of the killings were solidly grounded in international law. And others may have violated the Fifth Amendment, international law, or the laws of war.

In the past, Brennan has been willing to lie about those drone strikes to hide ugly realities. For example, he stated in the summer of 2011 that there had been zero collateral deaths from covert U.S. drone strikes in the previous year, an absurd claim that has been decisively debunked. What if he grew more forthright, either in public statements or by anonymously leaking information?

Recall how intimately Obama involved himself in many killings:

President Obama, overseeing the regular Tuesday counterterrorism meeting of two dozen security officials in the White House Situation Room, took a moment to study the faces .... Mr. Obama has placed himself at the helm of a top secret “nominations” process to designate terrorists for kill or capture, of which the capture part has become largely theoretical.

And the central a role Brennan played:

Beside the president at every step is his counterterrorism adviser, John O. Brennan, who is variously compared by colleagues to a dogged police detective, tracking terrorists from his cavelike office in the White House basement, or a priest whose blessing has become indispensable to Mr. Obama...

Finally, recall the chilling logic these two settled on:

Mr. Obama embraced a disputed method for counting civilian casualties that did little to box him in. It in effect counts all military-age males in a strike zone as combatants, according to several administration officials, unless there is explicit intelligence posthumously proving them innocent.

Even if Brennan told everything he knew, I'd still guess that the odds would be heavily against Obama ever finding himself on trial for civil-rights violations or war crimes (though if I were Obama, I'd take proactive steps to lessen the odds further.)

But I can imagine details that could cause Obama's image to suffer, now and in the eyes of history. He might be subject to travel bans or indictments in absentia in certain countries, for example. We don't now know what sort of legal authority Obama had the first time he ordered Anwar al-Awlaki to be killed, or why his 16-year-old son, an innocent American teenager searching abroad for his absentee father, ended up dead. There's still much classified information about innocent people killed in drone strikes.

I am not suggesting that Brennan is blackmailing Obama, or even that he would necessarily retaliate if fired. Still, if Obama is like most people in positions of power, he fires no subordinate without first asking himself, "Could this person damage me?" If Obama is a normal person, rather than an unusually principled person, the answer factors into his decision. Look at what Brennan said in March, immediately after denying that the CIA spied on the Senate Intelligence Committee, when Andrea Mitchell asked if he'd resign his post if that turned out to be wrong:

... if I did something wrong, I will go to the president, and I will explain to him exactly what I did, and what the findings were. And he is the one who can ask me to stay or to go.

He's a smart man.

All this may be irrelevant to his continued tenure. Perhaps Obama has always believed and continues to believe that Brennan is doing a heckuva job. But just as secret torture acted as a cancer on the U.S. government, encompassing acts so barbaric and criminal that, even recently, the CIA spied on a Senate subcommittee investigating the subject, America's semi-secret policy of semi-targeted killing rendered everyone involved complicit in activities sufficiently dubious that all desire their secrecy. Would you fire a guy who knows as much about your most morally fraught acts as Brennan knows about who Obama has killed in secret? Yeah, me neither. This isn't the biggest cost of presidents who hide arguably illegal actions by declaring them state secrets. But it is certainly one of the costs.

There's inevitably a need to review the job performance of people party to these secrets. They typically keep their jobs. So George W. Bush left us a CIA staffed partly with people willing to torture, and Obama will likely leave us with a CIA that includes torturers, people willing to kill American citizens in secret without due process, and people willing to spy on their Senate overseers. The Senate intelligence committee was established precisely to stop this sort of thing from playing out, but it is failing in its duties, as yesterday's crimes spawn today's efforts to spin or suppress those crimes. If the Senate doesn't act now to rein in the CIA, what will it take?