Yemen is the place to start. The sale of U.S. arms to the Saudis is enabling Mohammed bin Salman’s ill-judged intervention. The Saudi claim that American precision-guided missiles would reduce civilian casualties has not been borne out. It is not clear that the Saudis care very much about these casualties, though it is occasionally useful for them to pretend that they do. Congress could invoke the Arms Export Control Act, pass a joint resolution disapproving additional arms sales, and dare the president to veto it.

An additional option, not exclusive of the first, is exercising the old-fashioned power of the purse. In its next defense authorization bill, Congress could limit the use of appropriated funds for Yemen-related operations. Without U.S. refueling missions and other support activities, the Saudi military effort eventually would grind to a halt.

This exercise of congressional responsibility would have a dual purpose: to end U.S. complicity in a moral and humanitarian disaster, and to send a credible message to Saudi leaders that the U.S. will no longer give them a blank check in the region—nor for their dismal domestic record on human rights.