Yes. A U.S. grade can only be applied by a U.S. grader who is an employee of the U.S. Department of Agriculture. The Canadian packing companies would be glad to pay to have U.S. graders here in Canada, very much as there is U.S. Customs pre-clearance at Canadian airports. They'd have to pay for that service and they'd be glad to pay for it.
On May 11th, 2017. See this statement in context.