https://www.vice.com/en_us/article/wxjq8w/us-says-russia-leaving-nuclear-treaty-violates-nuclear-treaty

The U.S. State Department has said that Moscow can’t just leave the last remaining nuclear weapons treaty between Russia and the U.S. if it wants to. Unilaterally leaving the treaty, it said, is a violation of the treaty itself. According to Washington, Russia is still bound by the treaty even if it said it’s not.

“Russia’s claimed suspension of the New START Treaty is legally invalid,” the U.S. State Department said in a statement released on Wednesday. “As a result, Russia remains bound by its obligations under the treaty.”