I understand the anxiety. The rhetoric has been heated. As heated as it's been in the United States, it's been welcoming in Canada, so I understand that.
However, my answer on that question is that our customs and border patrol officers are extraordinarily professional. They're extraordinarily well trained. Also, they are public servants, so they serve not at the pleasure of any particular administration; this is their career, and they know a lot about what they're supposed to do in their job.
As you rightly point out, the proposed travel ban is being held up in court, so our system of constitutional democracy is working. The President isn't above the law and, regardless of his rhetoric, our system is working and our officials are acting as they should.
In terms of the question of approaching the border and not being able to turn away, I think people just have to get used to deciding a bit earlier whether they want to go. If you're going to change your mind, do it before you enter the zone, if you will, and then you can leave without any further questioning. Again, it's a trade-off. Do you want to come into the United States to do business, or travel, or vacation—and the same in the United States for Canada—or not? It's your choice, but it's also important to recognize how closely our countries work together.