Russia—and China—had seemed to benefit from the Houthis’ attacks on shipping in the Red Sea because the militia spared their ships. But it turns out that Moscow has been more than a passive beneficiary. As the Wall Street Journal recently reported, Russia has been providing the Houthis with targeting data for their attacks. Now that Russia has crossed this red line of actively aiding attacks on Western shipping, other hostile states may start sharing military-grade data with proxies of their choice.

One of the U.N. Security Council’s five permanent members is actively supporting attacks on global shipping. It’s a stark violation of the maritime rules, which grant merchant vessels the freedom and right to sail not only on the high seas but also through other countries’ waters and through internationally recognized straits without having to fear, let alone experience, acts of aggression.

Russia—and China—had seemed to benefit from the Houthis’ attacks on shipping in the Red Sea because the militia spared their ships. But it turns out that Moscow has been more than a passive beneficiary. As the Wall Street Journal recently reported, Russia has been providing the Houthis with targeting data for their attacks. Now that Russia has crossed this red line of actively aiding attacks on Western shipping, other hostile states may start sharing military-grade data with proxies of their choice.

One of the U.N. Security Council’s five permanent members is actively supporting attacks on global shipping. It’s a stark violation of the maritime rules, which grant merchant vessels the freedom and right to sail not only on the high seas but also through other countries’ waters and through internationally recognized straits without having to fear, let alone experience, acts of aggression.

The Houthis, you’ll remember, began their campaign against merchant vessels in the Red Sea last November, when they struck a string of vessels linked to Israel, supposedly in support of the people of Gaza. When the........

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