On Friday, a front-page New York Times story reported that a rift has emerged within the Obama Administration over whether it has authority to kill “rank-and-file” Islamist militants in foreign countries in which there is not an internationally recognized “armed conflict.” The implications of this debate are not trivial: Imagine that Russia started killing individuals living in the United States with remote-controlled drone missiles, and argued that it was justified in doing so because it had determined, in secret, that they posed a threat to Russia’s security, and that the United States was unwilling to turn them over. Would we calmly pronounce such actions compliant with the rule of law? Not too likely.

And yet that is precisely the argument that the Obama Administration is now using in regard to American’s own actions in places like Yemen and Somalia—and by extension anywhere else it deems militant anti-US groups may be taking refuge. On the same day the Times article appeared, John Brennan, President Obama’s senior advisor on homeland security and counterterrorism, gave a speech at Harvard Law School in which he defended the United States’ use of drones to kill terrorists who are far from any “hot battlefield.” Brennan argued that the United States is justified in killing members of violent Islamist groups far from Afghanistan if they pose a threat to the United States, even if the threat is not “imminent” as that term has traditionally been understood. (As if to underscore the point, The Washington Post reports that the US has “significantly increased” its drone attacks in Yemen in recent months, out of fears that the government may collapse.)

In international law, where reciprocity governs, what is lawful for the goose is lawful for the gander. And when the goose is the United States, it sets a precedent that other countries may well feel warranted in following. Indeed, exploiting the international mandate to fight terrorism that has emerged since the September 11 attacks, Russia has already expanded its definition of terrorists to include those who promote “terrorist ideas”—for example, by distributing information that might encourage terrorist activity— and to authorize the Russian government to target “international terrorists” in other countries. It may seem fanciful that Russia would have the nerve to use such an authority within the United States—though in the case of Alexsander Litvinenko it appears to have had few qualms about taking extreme measures to kill an individual who had taken refuge in the United Kingdom. But it is not at all fanciful that once the US proclaims such tactics legitimate, other nations might seek to use them against their less powerful neighbors.

Ironically, Brennan’s speech lauded the benefits of fighting terrorism within the confines of the rule of law. When we uphold the rule of law, Brennan argued, “our counterterrorism tools are more likely to withstand the scrutiny of our courts, our allies, and the American people,” and to offer “a powerful alternative” to al Qaeda’s lawless ways. Indeed, as I argue in the current issue of The New York Review, the Obama administration deserves credit—along with civil society and the courts—for helping to restore the rule of law, at least partially, after the blatant disregard with which its predecessor dismissed it in the immediate aftermath of September 11.

Yet as the New York Times report makes clear, when it comes to targeted killings, there is serious dispute, even within the administration, about what the law permits. . Some, like State Department legal advisor Harold Koh, take the position that beyond the battlefield, we can attack only those “high-value individuals” who are actually engaged in plotting attacks on the United States, and only where their threats are specific enough to allow the US to claim the right to self-defense granted to all states under the UN Charter. The Charter permits nations to use unilateral military force only in self-defense against an armed attack, and has been interpreted to permit self-defense against threatened attacks only when they are imminent.. Defense Department lawyers maintain, by contrast, that the ongoing war against al-Qaeda authorizes us to kill any of the thousands of rank and file members not only of al-Qaeda itself, but also of al-Qaeda in the Arabian Peninsula—a Yemen-based group founded in 2009—and of al-Shabab, a Somalia-based militant group. Although both of the latter organizations were founded well after the September 11 attacks, the Defense Department considers them fair game because it deems them to be associated with al Qaeda.

In his Harvard speech, Brennan deftly avoided siding with either contending position. He insisted that the administration’s policy is “focused on those individuals who are a threat to the United States, whose removal would cause a significant—even if temporary—disruption of the plans and capabilities of al-Qaeda and its associated forces.” But note his use of the words “focused” and “associated forces.” He did not say that the administration’s targeting authority was limited to such individuals, only that for the moment that is where the US’s strategic focus lies. And he did not define what counts as an “associated force.” Is the US’s desire to disrupt temporarily the capabilities of al Shabab, a group largely consumed by an internal conflict in Somalia, enough to justify killing a high-ranking member (let alone the “rank and file”) with a drone, even if neither the individual nor the group is poised to attack us? Brennan’s formula seemed to suggest as much. And published accounts report that the US has indeed attacked al Shabab members with drones in Somalia.

Brennan further argued that the UN Charter requirement that a threat be imminent before a nation can exercise its right of self-defense makes less sense when a country faces a threat from a clandestine terrorist group, whose threats may be harder to spot in advance. But the purpose of that requirement was to ensure that military force is truly a last resort. Too many wars have been launched on the basis of ill-defined future threats. The watered-down imminence that Brennan seemed to advocate, especially when coupled with his suggestion that even a temporary disruption of “capabilities” is sufficient reason to strike, would seem to permit targeting even where no attack is in fact imminent. Such reasoning could also be used to justify lethal force in cases where it might well be possible to foil a possible attack through arrest, criminal prosecution, interdiction, or other means. As many countries, including Great Britain, Germany, Spain, and, Italy have shown, the fact that organized groups seek to engage in politically motivated violence does not necessitate a military response.

The legal parameters defining the use of military force against terrorists are unquestionably difficult to draw. On the one hand, no one disputes that it is permissible to kill an enemy soldier on the battlefield in an ongoing armed conflict. On the other hand, absent extreme circumstances, constitutional and international law bar a state from killing a human being in peacetime without a trial (and even then, many authorities hold that capital punishment violates international human rights law). Al-Qaeda has not limited its fight to the battlefield in Afghanistan, and most agree that, as long as sovereignty concerns are met, the use of military force can follow this enemy beyond the battlefield at least in some situations. Killing Osama bin Laden in Pakistan—whose tribal areas are for all practical purposes part of the theater of war—was the justified targeting of the enemy’s leader. But are al-Qaeda in the Arabian Peninsula or al-Shabab the same “enemy,” or merely sympathetic adherents of a terrorist philosophy? They certainly did not attack us on September 11, nor are they harboring those who did. Can we summarily execute all terrorists who we fear might someday commit a terrorist act against us? Brennan’s speech offered no answers.

And that makes it especially disturbing that the contours of US policy and practice in this area remain largely secret. Presumably the administration has developed criteria for who can be killed and why, and a process for assessing who fits those criteria and when their targeting is justified. But if so, it hasn’t told us. Instead, it exercises the authority to kill, not only in Afghanistan and the border regions of Pakistan, but in Yemen,Somalia, and presumably elsewhere, based on a secret policy. We learn more about its outlines from leaks to The New York Times than from the cryptic comments of US officials in speeches like Brennan’s. If we are engaging the enemy within the rule of law, as Brennan insisted we must, we should have the courage to make our policies transparent, so that the people, both in the United States and beyond, can judge for themselves. And if, by contrast, we continue to justify such practices in only the vaguest of terms, we should expect other countries to take them up—and almost certainly in ways we will not find to our liking.