As Donald Trump assumes office today, he inherits a targeted killing program that has been the cornerstone of U.S. counterterrorism strategy over the past eight years. On January 23, 2009, just three days into his presidency, President Obama authorized his first kinetic military action: two drone strikes, three hours apart, in Waziristan, Pakistan, that killed as many as twenty civilians. Two terms and 540 strikes later, Obama leaves the White House after having vastly expanding and normalizing the use of armed drones for counterterrorism and close air support operations in non-battlefield settings—namely Yemen, Pakistan, and Somalia.

Throughout his presidency, I have written often about Obama’s legacy as a drone president, including reports on how the United States could reform drone strike policies, what were the benefits of transferring CIA drone strikes to the Pentagon, and (with Sarah Kreps) how to limit armed drone proliferation. President Obama deserves credit for even acknowledging the existence of the targeted killing program (something his predecessor did not do), and for increasing transparency into the internal processes that purportedly guided the authorization of drone strikes. However, many needed reforms were left undone—in large part because there was zero pressure from congressional members, who, with few exceptions, were the biggest cheerleaders of drone strikes.

On the first day of the Trump administration, it is too early to tell what changes he could implement. However, most of his predecessor’s reforms have either been voluntary, like the release of two reports totaling the number of strikes and both combatants and civilians killed, or executive guidelines that could be ignored with relative ease. Should he opt for an even more expansive and intensive approach, little would stand in his way, except for Democrats in Congress, who might have newfound concerns about the president’s war-making powers. Or perhaps citizens and investigative journalists, who may resist efforts to undermine transparency, accountability, and oversight mechanisms.

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Less than two weeks ago, the United States conducted a drone strike over central Yemen, killing one al-Qaeda operative. The strike was the last under Obama (that we know of). The 542 drone strikes that Obama authorized killed an estimated 3,797 people, including 324 civilians. As he reportedly told senior aides in 2011: “Turns out I’m really good at killing people. Didn’t know that was gonna be a strong suit of mine.”