Congress is mostly a media circus these days, so credit the members who take their duties seriously. Lawmakers are doing a public service by trying to get to the truth on whether the Trump Administration killed defenseless survivors of a drug-boat strike.

The controversy involves a Washington Post report that Defense Secretary Pete Hegseth ordered that no one survive a Sept. 2 missile strike on an alleged drug boat in the Caribbean. The story cites unidentified sources claiming that the U.S. military, on Mr. Hegseth’s orders, conducted a second strike to finish off survivors clinging to the destroyed boat.

Mr. Hegseth called the story “fabricated, inflammatory and derogatory,” and said U.S. actions have been “in compliance with the law of armed conflict–and approved by the best military and civilian lawyers, up and down the chain of command.”

President Trump added Sunday that the Secretary “said he did not say that, and I believe him, 100%.” Mr. Trump added that he’ll “look into it, but no, I wouldn’t have wanted that, not a second strike.”

The Pentagon is certainly full of people who might leak a derogatory story because they’d like to see Mr. Hegseth fired. The U.S. campaign against drug boats has also riled civil libertarians and progressives who want to constrain the President’s ability to conduct military action.

But the charge of deliberately killing the defenseless is serious enough to warrant a close look from Congress. That includes Mr. Hegseth giving an account under oath. The Administration so far seems to think it can ride out the story with ritual denunciations of the media.

If Mr. Hegseth is right, then the factual record will support him. There are layers of bureaucracy between the Secretary of Defense and the business end of a missile. You can bet senior military officers bought insurance on their own careers by recording the advice they gave and the directions they received.

Our view is that the Commander in Chief deserves legal latitude as part of his constitutional war powers. But that doesn’t extend to shooting the wounded in violation of U.S. and international rules of war. The Pentagon’s own law of war manual prohibits “hostilities on the basis that there shall be no survivors.” Such excesses will also turn the public against allowing a President the power he may someday need to defend the country’s interests quickly.

The Hegseth story has additional currency because the Administration isn’t explaining its aims in the Caribbean with either voters or Congress. Sens. Roger Wicker and Jack Reed of the Senate Armed Services Committee, have been writing to the Pentagon asking for more details on the legal rationale for its drug-boat strikes. They seem to get mostly a stonewall.

That’s all the more reason for Congress to learn the truth about the Hegseth story, and some are ready to do so. Reps. Mike Rogers (R., Ala.) and Adam Smith (D., Wash.), the top members on the House Armed Services Committee promised in a statement over the weekend “bipartisan action to gather a full accounting of the operation in question.” The Senate Armed Services Committee also promised an inquiry.

The drug-boat war is presenting questions of presidential power and America’s role in the world that will continue long after President Trump leaves Washington, and good for lawmakers who appreciate the stakes.

–The Wall Street Journal