While it's tempting to say that this is simply a matter within U.S. sovereignty, as I alluded to earlier, even within the realm of its sovereignty, the U.S. is a party to the ICCPR. While that treaty cannot be invoked by private citizens in U.S. courts, I think it is entirely appropriate and proper for other parties to that treaty, such as Canada, to raise questions with the United States as to whether what is being demanded by the U.S. is consistent with the quite detailed standards that have been adopted by the UN Human Rights Committee for measures that implicate the right to freedom of movement guaranteed by article 12 of the ICCPR.
I would not be so ready to say that Canada has to cede to the U.S. the power, within its own territory, to abrogate its commitments to black letter international human rights treaty law. I think this is the kind of discussion that could go on in the context of diplomatic negotiations over existing treaty commitments as well as for a possible future treaty in this area.