This remarkable Wall Street Journal story came out over Yom Kippur, so I'm late in commenting on it. But it's worth everyone's attention. It opens:
About once a month, the Central Intelligence Agency sends a fax to a general at Pakistan's intelligence service outlining broad areas where the U.S. intends to conduct strikes with drone aircraft, according to U.S. officials. The Pakistanis, who in public oppose the program, don't respond.
On this basis, plus the fact that Pakistan continues to clear airspace in the targeted areas, the U.S. government concludes it has tacit consent to conduct strikes within the borders of a sovereign nation, according to officials familiar with the program.
Representatives of the White House's National Security Council and CIA declined to discuss Pakistani consent, saying such information is classified. In public speeches, Obama administration officials have portrayed the U.S.'s use of drones to kill wanted militants around the world as being on firm legal ground. In those speeches, officials stopped short of directly discussing the CIA's drone program in Pakistan because the operations are covert.
Now, the rationale used by the administration, interpreting Pakistan's acquiescence as a green light, has set off alarms among some administration legal officials. In particular, lawyers at the State Department, including top legal adviser Harold Koh, believe this rationale veers near the edge of what can be considered permission, though they still think the program is legal, officials say.
The story---by Adam Entous, Siobhan Gorman, and Evan Perez---reports that Pakistani officials used to acknowledge receipt of the faxes and clear the airspace. Now, amid public and private objections to drone strikes, they don't acknowledge receipt of the faxes, but they do still clear the airspace. The United States takes this as implied consent, presumably because Pakistan does nothing to stop the activity, flagrantly conducted, over a long period of time. It doesn't respond to the faxes by saying, "no, you can't do that." It not only doesn't shoot down the drones---something that would be easy to do---it gets out of their way. So clearly, there's a decision of sorts to submit to, if not to accept, the incursions. As I say in the piece, this lies at the margins of what can reasonably be construed as consent.
A few thoughts:
In many ways, the CIA here is only behaving towards Pakistan the way it behaves every day in briefing Congress on covert actions. Members of Congress listen to briefers and often stay silent so as to be able to criticize the operation if it goes bad and not be too implicated in it. The CIA, in turn, has learned to consider such silence to be the intelligence committees' consent: The agency, after all, has given the committees the information they need to stop a program and they have not acted to do so. Here it is really treating the ISI the same way. (Never mind that the if the Pakistanis acted to stop the strikes, the U.S. would probably consider that evidence that the country was unwilling or unable to stop terrorist activity emanating from Pakistan's soil---and consider that to be legal grounds for U.S. unilateral action on Pakistani territory.)
In other contexts, of course, this sort of implied acquiescence clearly doesn't count as consent. Consider a college dorm room where the issue is whether a sexual encounter had been consensual or not. We do not accept the explanation from a young man in such an encounter who, despite the vociferous objections of the young woman, declares: "well, I told her very clearly what I was going to do and she didn't stop me, so 'no' clearly meant 'yes'"---which is roughly what the United States is saying of Pakistan here.
On the other had, there's a long history in property rights disputes of flagrant assertions of right leading to legally recognizable claims--squatters who acquire residency rights, residents who over time acquire title, and the like. So whether implied consent has any legs is highly dependent on context.
For what it's worth, I think it's going to be hard over time to sustain U.S. action in Pakistan based on an implied consent theory in the face of explicit non-consent---however insincere.