The Trump administration has launched a challenge under USMCA governance rules against Canadian dairy tariff-rate quotas. That’s the first formal challenge since USMCA came into force in July. There will be up to 45 days of negotiations after which the process will enter arbitration. Assuming no early capitulation from Canada it’s likely that the Biden administration will have to handle the fallout. Canada only accounted for 4.8% of U.S. dairy exports in the 12 months to Oct. 31 versus Mexico’s 26.8%. Shipments to both have fallen recently. China meanwhile has come t...