Click to expand Image The burned remains of a fuel tanker in Arhab at the site of the water drill attack in the Sanaa governorate. The well under construction was meant to supply Beit al-Saadan, a nearby village, with water. Human Rights Watch found no evidence of military operations or materiel at the site. © 2016 Kristine Beckerle/ Human Rights Watch

A well being dug in a small village in Yemen was nearing completion last September when it was bombed by the Saudi Arabia-led coalition. The bomb hit the workers’ shelter, killing six men and wounding five others. When village residents went to help, the aircraft struck again. In all, at least 31 civilians, including 3 boys, were killed and 42 wounded. The well, which villagers had pooled their money to drill, was destroyed.

I went to the bombing site with friends and family members of the victims. In the wreckage, we found a piece of a US-made munition with markings indicating it was manufactured by Raytheon in October 2015. It was the 23rd time Human Rights Watch had identified remnants of US-supplied weapons at the site of an apparently unlawful coalition attack, the fourth time we identified a weapon made by Raytheon.

Now, the Trump administration appears poised to approve the sale of more weapons to Saudi Arabia, including Raytheon-made bombs, to the tune of $400 million.

Since March 26, 2015, the Saudi-led coalition has carried out military operations in Yemen in an effort to restore Yemeni President Abdu Rabbu Mansour Hadi to power. In the process, they’ve bombed schools, homes, markets and hospitals. The parties they are fighting—the Houthis and forces loyal to the former president, Ali Abdullah Saleh, who was deposed in 2011 following popular uprisings—have also repeatedly violated the laws of war.

At least 4,773 civilians have been killed and 8,272 wounded since the start of the conflict, the majority by coalition airstrikes, according to the United Nations human rights office. The war has driven Yemen to the humanitarian “brink,” with 7 million people facing starvation and more than two-thirds of the population in need of humanitarian aid. Both parties have blocked or restricted critical relief supplies from reaching civilians.

Click to expand Image Markings on a remnant of a CBU-58 cluster bomb found near al-Zira`a Street in Sanaa on January 6, 2016 indicating that it was manufactured in 1978 at the Milan Army Ammunition Plant in the US state of Tennessee. © 2016 Private

The United States, which became a party to the Yemen conflict during the first months of fighting by providing direct support to the coalition, including refueling planes during bombing raids, has provided substantial assistance to Saudi Arabia, including “intelligence, airborne fuel tankers and thousands of advanced munitions.” International legal scholars and US lawmakers have warned that continued US support—including through weapons sales—to Saudi Arabia’s military campaign in Yemen may not only make the US government complicit in coalition violations of the laws of war, but also expose US officials to legal liability for war crimes.

The Sierra Leone war crimes tribunal, in a decision the US military commissions prosecutor endorsed in 2013, ruled that for an individual to aid and abet a war crime, they must provide practical assistance that has a “substantial effect” on the commission of a crime; and know or be aware the assistance has a “substantial likelihood” of aiding that crime.

The US has for many years sold arms to Saudi Arabia. The Saudi-led coalition has used these weapons in its Yemen attacks, including two of the war’s deadliest for civilians—on a crowded market and a funeral hall full of people—both of which appear to have been war crimes.

For U.S. officials providing assistance to be guilty of aiding and abetting coalition war crimes, they must be “aware” of the “substantial likelihood” their aid would be used to assist unlawful attacks, and that the forces they were assisting intended to commit war crimes. A US State Department lawyer, writing in his personal capacity, has made the same point, using assistance to the Syrian government as an example.

Last month, an apparent coalition helicopter attacked a boat filled with Somali refugees and migrants who were fleeing Yemen in search of safety. Instead they found themselves at sea, at night, attacked from above. At least 33 died and 27 were injured. While it is still not clear which coalition member attacked the boat, the State Department has approved licenses for the sale or servicing of military helicopters to Saudi Arabia, the United Arab Emirates, Kuwait, and Jordan, all coalition members. The day before the attack, the Defense Department announced Boeing had been awarded a $3.2 billion contract to sell Saudi Arabia more military helicopters.

While many of the weapons in Saudi Arabia’s arsenal were obtained long before the coalition began its military operations in Yemen in March 2015, US officials should have been aware by late 2015 of the coalition’s numerous attacks that violate the laws of war. Many were reported by the United Nations, as well as human rights organizations. U.S. officials debated internally whether US support to the coalition could make US personnel criminally liable, and the State Department’s top human rights officer under President Barack Obama conceded a “possibility of legal jeopardy for US officials if sales continue despite continuing evidence of violations of the laws of war.”

As the armed conflict in Yemen continues and evidence of war crimes mounts, legal risk for U.S. officials will only increase.

Click to expand Image Remnant of a wing assembly that is mounted on a US-made GBU-12 Paveway II laser-guided 500-pound bomb found at the Arhab water drilling site, Sanaa governorate, where at least 31 civilians were killed in an airstrike on September 10, 2016. According to the manufacturing date as well as the national stock number, this wing assembly was produced by Raytheon Company, a US defense contractor, in October 2015. © 2016 Priyanka Motaparthy / Human Rights Watch

By October 2015, when the weapon used in the strike on the well was manufactured, Human Rights Watch and others had reported on a number of unlawful coalition airstrikes. More than two years into the war, we’ve documented 81 apparently unlawful coalition attacks and almost two dozen in which US weapons were used. For weapons produced later and shipped now, pleading ignorance is no longer plausible.

Some US lawmakers are pushing the Trump administration to curb weapons sales to Saudi Arabia and demand more transparency about how US munitions are used. On April 6, several senators introduced a bipartisan bill to limit US arms transfers to Saudi Arabia, requiring the White House to certify that Saudi Arabia was taking all feasible precautions to minimize civilian casualties and to brief Congress on whether Saudi Arabia had used US weapons in unlawful Yemen attacks. The same day, a letter signed by 31 members of Congress called on the Pentagon to release more details about Saudi-led coalition violations.

There is no mystery here: The Saudi-led coalition has committed scores of unlawful attacks, many amounting to war crimes. Continued arms sales not only send a clear message to the coalition that it can kill civilians with impunity, but they increasingly put US officials at legal risk for aiding those crimes.