Saudi Arabia’s Crown Prince Mohammed bin Salman is pictured while meeting with the Tunisian president at the presidential palace in Carthage on the eastern outskirts of Tunis on Nov. 27. (Fethi Belaid/AFP/Getty Images)

PRESIDENT TRUMP’S craven abdication in the case of murdered Saudi journalist Jamal Khashoggi obligates other Americans, including Congress and the business and nonprofit worlds, to defend the country’s fundamental values. They must insist that the truth about this state-sponsored murder be revealed, and that its authors — who the CIA believes include Crown Prince Mohammed bin Salman — be held accountable. A failure to do so would cause profound damage to vital U.S. interests, including the long-term relationship with Saudi Arabia.

The Senate could get a first chance to act this week on a War Powers Resolution measure to end U.S. support for the disastrous Saudi-led intervention in Yemen. A similar measure failed by six votes this past spring; since then, the humanitarian catastrophe unleashed by Saudi bombing and an air and naval blockade has only intensified. As we have previously argued, cutting off U.S. aid for the war would be a good first step to reset U.S. relations with Mohammed bin Salman’s reckless and destructive regime. But passing an invocation of the War Powers Resolution may not accomplish that aim, as it could be blocked by the House or by President Trump.

The Republican and Democratic leaders of the Senate Foreign Relations Committee, Bob Corker (Tenn.) and Robert Menendez (N.J.), respectively, have sent the White House a letter requiring it to determine Mohammed bin Salman’s responsibility in the Khashoggi murder under the Global Magnitsky Act, which provides a mechanism for punishing human rights violations. That, too, could be sidestepped by the administration, which already met one congressional mandate by falsely certifying that Saudi forces were taking steps to avoid further civilian casualties in Yemen. Our bet is that the response to the senators will be a version of Mr. Trump’s “maybe he did and maybe he didn’t,” even though legislators who have seen the CIA’s reporting say that that is dishonest.

A better way forward would be attaching a provision to a must-pass budget bill ending military aid to Saudi Arabia until the Yemen war ends and all authors of the Khashoggi murder are identified and sanctioned. Sen. Lindsey O. Graham (R-S.C.) has hinted at such a budget amendment, as has Mr. Corker. It’s time they and other Republicans, such as Sens. Susan Collins (Maine) and Joni Ernst (Iowa), act on their strong statements of outrage over the Khashoggi murder and Mr. Trump’s response to it.

Meanwhile, U.S. businesses, universities, think tanks and lobbying firms that have done business with Saudi Arabia must rethink those ties. Many responded to the Khashoggi murder by suspending relations or promising to reconsider them. If Mr. Trump had acted in the U.S. interest by imposing meaningful consequences on Mohammed bin Salman and his regime, he could have cleared the way for a gradual rebuilding of normal relations. His failure to do so means business as usual cannot resume.

As long as he dodges accountability for a state-sponsored murder, Mohammed bin Salman should be treated as a pariah by all those who value human rights and the rule of law. His initiatives should be shunned, and statesmen from the democratic world should not meet with him. The crown prince is traveling to Buenos Aires this weekend for the Group of 20 summit; the leaders attending there can distinguish their principles from those of Mr. Trump by refusing to pretend that nothing is amiss.