A WTO arbitrator ruled today that Mexico can retaliate in the Tuna/Dolphin dispute:
7.1. For the reasons set out above, the Arbitrator determines that the level of nullification or impairment of benefits accruing to Mexico as a result of the 2013 Tuna Measure is USD 163.23 million per annum. Therefore, in accordance with Article 22.4 of the DSU, Mexico may request authorization from the DSB to suspend concessions or other obligations as indicated in document WT/DS381/29 at a level not exceeding USD 163.23 million per annum.
Obviously, the imposition of this retaliation needs DSB authorization first. Also, there is an Article 21.5 panel that will rule soon on whether the subsequent U.S. compliance measure is consistent with WTO rules, which would, I think, de-authorize the retaliation. But let's assume that Mexico moves forward now with the process of imposing $163 million of authorized retaliation against the U.S. imports. How will the Trump administration react? You can imagine that some people in the administration will not be happy about it. But you can also imagine that some people in the administration would be excited to have an excuse to repeal the regulation in question. Presumably the Mexicans are aware of this, so maybe it's possible that this dispute does not get splashed across the headlines as the lumber tariffs currently are, and the parties quietly work out an agreement behind the scenes.
ADDED: To clarify, I mentioned the possibility of "repealing the regulation," but I recognize there is a court ruling on these issues as well, so the Trump administration will not have unlimited discretion. But they may be eager to look for creative ways to ease the regulatory burden on all the private actors involved.