CNN broke an important story today outlining how Saudi Arabia and the United Arab Emirates (UAE) have intentionally transferred American-made weapons to violent non-state actors. Intended as a government to government sale, everything from American rifles to Oshkosh armored vehicles to TOW anti-tank missiles have made their way into the hands of “Al Qaeda-linked fighters, hard-line Salafi militias, and other factions waging war in Yemen.”

Although the extent of the problem in Yemen is disturbing, the illegal dispersion of American weapons is nothing new. And the fact that Saudi Arabia and the UAE are unreliable customers should not come as any surprise.

American experience in the Middle East has long demonstrated that sending weapons into conflict zones is a recipe for trouble. After the U.S. invasion of Iraq, for example, the United States provided Iraq with a vast amount of weapons and equipment in order to rebuild the Iraqi army. Later, however, the Islamic State (ISIS) wound up with almost an entire division’s worth of American equipment after defeating the Iraqi army in 2014, helping fuel its emergence. This equipment found its way into Syria, where ISIS also stole American-supplied rockets just weeks after they were sent to arm Syrian rebels fighting ISIS and Assad.

Nor is the problem of dispersion limited to the battlefield. American weapons often wind up crossing national borders to be sold to the highest bidders on the black market. The CNN report notes that Yemeni black markets are showcasing American weapons, but so are markets in Somalia, South Sudan, Mali, Cote d-Ivoire, and Latin America.

Losing weapons to adversaries and criminals makes life difficult enough. What makes the Yemen case particularly troublesome is the fact that Saudi Arabia and the UAE felt free to give up control over American weapons on purpose. The Saudi coalition hoped to gain traction and support from the militias in the complex political landscape of the protracted conflict. The fact that such transfers were technically illegal meant little.

Though arms sales advocates argue that selling weapons to allies will allow the United States to influence their behavior, Yemen illustrates the exact opposite. When arms sales customers have more immediate concerns in their own backyard, their willingness to take direction from Washington, D.C. dwindles.

Policy makers should take this report as an opportunity to rethink U.S. arms sales policy. As we have shown in previous research, these challenges are not impossible to predict. Some countries to which the United States transfers weapons, like Saudi Arabia, Egypt, Afghanistan, Sudan, and Iraq, represent greater risks for unintended negative consequences than others. A more prudent arms sales policy would acknowledge that promises and end-use monitoring are insufficient to prevent the misuse of American weapons abroad. In some cases, not selling weapons may be the only way to prevent downstream problems.