Riyadh is killing civilians with American help, and it’s jeopardizing the international credibility of the United States.

Across Republican and Democratic administrations, the United States has taken pride in standing by its friends and allies around the world when trouble commences. Acting side-by-side with allies in the Middle East, Europe, and Asia is often considered one of the bedrocks of a bipartisan U.S. foreign policy establishment; when a friend is in need or its security is threatened, the U.S. is quick to rise up and provide critical assistance often to the tune of billions of dollars.

That foreign policy tenet, however, is increasingly causing the United States more grief than benefit, particularly when America’s allies are engaging in activity that is at best questionable and at worst against international humanitarian law. Washington’s logistical aid to the Saudi-led Arab coalition fighting against the Houthis in Yemen fits that category perfectly.

An operation that was launched in March 2015 for a legitimate objective — defending the internationally recognized Yemeni government — has turned into a stalemate that has produced nothing but misery for millions of Yemeni civilians simply trying to survive. Yemen, already the Arab world’s poorest country before the war began, has been devastated in terms of economic productivity, political stability, and global health indicators.

The U.N. High Commissioner for Human Rights, the U.N. Security Council’s own Panel of Experts, and the U.N. Secretary-General have all reported over the past several months that Riyadh’s coalition of the willing is responsible for the bulk of Yemen’s deaths and injuries. In lieu of good-faith efforts to avoid civilians during the course of hostilities, Saudi forces have instead perpetrated deliberate violations of the international human rights and humanitarian law. In Sana’a alone, Saudi airstrikes have obliterated schools, hospitals, clinics, weddings, residential homes, and entire city blocks — all protected by the Geneva Conventions and the laws of war.

Through it all, however, the United States has continued to support Saudi Arabia in its Yemen campaign. U.S. aircraft have conducted surveillance on behalf of the coalition; sales of U.S.arms to the Saudis have been approved, the most recent of which included $1.29 billion in air-to-ground munitions; and the blocking or watering down of attempts in the U.N. Human Rights Council to establish an independent international commission of inquiry. The Obama administration has for all intents and purposes stood by Saudi Arabia, despite numerous reporters of misconduct towards civilians.

All of this begs a fundamental question that is far too often avoided in Washington: at what point does an alliance begin to jeopardize the international credibility and good name of the United States of America?

Whatever the merits of Riyadh’s intervention in Yemen, the fact remains that its conduct in the conflict over the past 16 months – and Washington’s association with it – is severely straining the kinds of relationships among ordinary Yemenis that the U.S. will undoubtedly need in the future if it wishes to implement a successful counterterrorism strategy in that country. It’s difficult to see how continuing to enable Saudi Arabia’s war from the air with the sale of more American munitions helps U.S. interests in that part of the world.

U.S. assistance to Saudi Arabia in Yemen has come about almost as a reflex. If Riyadh requests U.S. military capabilities, the U.S.agrees with barely any questions asked. This no-strings-attached aid, however, has merely made the situation in Yemen worse by providing the Saudis with the false sense of confidence that Washington’s unique military capacity will be available regardless of how it conducts the war. Besides keeping Al-Qaeda in check, there is very little reason for the United States to be taking sides in a civil war that doesn’t directly threaten America’s interests in the region.

For far too long, sustaining an alliance for alliance’s sake has been viewed in Washington as the overarching national security objective. It is far past time for the U.S. to take a good and hard look at which alliances actually serve U.S. national security interests and which alliances need to be refined based upon that ally’s behavior. The U.S. cannot afford to give its allies a blank check. If a nation wants America’s help, its leadership should lay out a case as to why America — and only America — can make a positive difference. More importantly, the United States must begin to demand those answers.