Tim Kaine actually said...
The last time I was in China talking at great length about the South China Sea with our counterparts, I said that we are in the ironic situation where the United States has not ratified the Law of the Sea, but we abide by it; China has ratified it, but ignores it.
Context
Kaine highlights the irony of U.S. adherence to a treaty it hasn't ratified while China ignores its ratified obligations.
04/26/2016