Donald Trump loves to present himself as the anti-Obama. But this week, when he handily vetoed a congressional resolution directing him to end U.S. military support for the Saudi-led coalition war in Yemen, he leaned heavily upon his predecessor’s policies—an inconvenient fact for both presidents’ supporters.

For the past four years, a coalition of 10 countries led by Saudi Arabia and the United Arab Emirates has conducted a massive bombing campaign and an aerial and naval blockade of Yemen in an effort dislodge the Houthis, who took control of the country in 2014. This intervention, supported militarily from its first day by the United States, has produced what the UN has called “the worst manmade humanitarian crisis in the world.” Repelled by these effects and Saudi Arabia’s human rights violations—most recently the murder of journalist Jamal Khashoggi—Congress took the unprecedented step of directing the president to withdraw U.S. forces from an ongoing conflict.

The Congressional aides drafting the Yemen resolution that finally passed in early April specifically inserted an amendment in order to invoke the War Powers Resolution—a 1973 law passed over Richard Nixon’s veto that orders the president to withdraw U.S. forces from “hostilities” within 60 days absent congressional authorization. The amendment clarified that both mid-air refueling of Saudi jets and the provision of targeting intelligence in Yemen constitute involvement in “hostilities.” (Trump stopped the mid-air refueling of Saudi jets in November but continues to provide essential logistical support.)

But in his veto message, Trump denied this claim. A resolution demanding an end to American engagement in hostilities in Yemen is “unnecessary,” Trump argued, because the U.S. is, in fact, “not engaged in hostilities in or affecting Yemen,” aside from operations targeting al Qaeda in the Arabian Peninsula and ISIS, to which the resolution did not apply in the first place.

Trump’s ability to claim the U.S. is not engaged in hostilities in Yemen is based on an interpretation of “hostilities” taken directly from the Obama administration.