What are Britain, France, and Germany thinking? I ask that question because those three nations on Friday abstained in a U.N. Security Council vote on whether to extend an international arms embargo on Iran.

The abstention and associated defeat of a U.S. call to extend the embargo means that Iran will soon be able to buy foreign military equipment on the open market. In turn, Iran will soon be able to make significant advances to its ballistic missile and air defense network forces. This will enable its posing of a steadily escalating threat to the region and the world. While the Trump administration now says it will trigger a “snapback” sanctions mechanism under the 2015 Joint Comprehensive Plan of Action nuclear agreement, it’s far from clear whether that tactic will achieve anything. After all, if China, Russia, Britain, and the European Union refuse to recognize the snapback, its impact will be muted. At that point, the only alternative will be for the United States to introduce secondary sanctions on foreign entities that sell arms to Iran.