Retroactive Law-Making under GATT Article X

Those of you who follow Scott Lincicome's blog have no doubt seen his discussion of the U.S. court appeal relating to the recent U.S. law that retroactively authorizes the U.S. Department of Commerce to apply countervailing duties on imports from "non-market economies" like China and Vietnam.  As one plaintiff put it:

Plaintiffs strongly disagree with the way in which Congress has applied parts of its new law retroactively. This selective retroactivity violates three fundamental principles of justice enshrined in the Constitution. First, the retroactivity provision singles out a particular group, and then condemns and punishes conduct by that group not illegal or punishable at the time it was committed, and in doing so violates the Ex Post Facto Clause of Article I. Second, even if the new law is not so punitive as to trigger the Ex Post Facto Clause, the retroactivity provision imposes wholly new taxes that dramatically burden importers with no notice, going back far beyond the limited period of retroactivity typically allowed with or without notice, and in doing so violates due process rights under the Fifth Amendment. Third, the retroactivity provision irrationally discriminates against past importers, refusing to give them the same rights and opportunities given to future importers, and in doing so denies equal protection of the laws also guaranteed by the Fifth Amendment.

Now China has made similar claims against the same aspects of the U.S. law under GATT Article X, in the DS449 WTO complaint:

by its express terms, Section 1 of P.L. 112-99 applies retroactively to actions and events that occurred prior to its official publication.

...

China considers that Section 1 of P.L. 112-99, including the new Section 701(f) of the Tariff Act which it establishes, is inconsistent as such with Articles X:1, X:2, and X:3 of GATT 1994. This is because, inter alia:

The legal standards are different, but the issues are similar.  It will be interesting to see how domestic courts and the WTO courts deal with the same measure, under different -- but at least somewhat related -- legal provisions.  And perhaps the U.S. court decision will play a role in the consideration at the WTO.