He is skeptical that a WTO complaint under GATT Article XV would be useful. From a WSJ op-ed:
The second possibility is that the U.S. would—as the new Congressional proposals also contemplate—sue China in the WTO alleging that China's exchange actions are inconsistent with China's international obligations under the WTO treaty. A provision in part of that treaty, the General Agreement on Tariffs and Trade, states that WTO Members "shall not, by exchange action, frustrate the intent of the provisions of" the treaty. This provision has been part of the GATT for more than 60 years, but it has never been the subject of dispute settlement. There is no clear understanding among WTO Members of what it means.
The legal challenge for the U.S. in bringing such a suit would be two-fold. The Obama administration would have to convince the WTO judges that the word "frustrate" in this provision means what the U.S. thinks it means. Furthermore, the U.S. would have the burden of proving that China has, by its exchange actions, caused such frustration.
And he also worries about the ramifications of a case:
... Does the U.S. want other members to claim that the new U.S. push for exports, coupled with low U.S. interest rates, is another form of currency manipulation?
