I mean, they definitely could in a legal sense, but then the reaction from the US would likely be extreme and putative, it would likely cause a huge shock to the Canadian economy, and it would risk a sharp decline in the legitimacy of the canadian government.
Shutting down trade would be stupid, but it wouldn't have any effect on the legitimacy of the government. We are pretty damn secure about the legitimacy of our electoral process.
This happens all the time, to famous and non-famous people. US citizens have no rights to enter Canada. Also the right to refuse people actually further legitimizes the Canadian Government.
yes, I totally understand that. While they are separate countries, their economies and supply chains are extremely closely tied together and closing the border to US people would cause an extreme econ shock in both countries. Retaliation from the US would probably be stupid, out of scale, and make the situation much worse. My whole point is I don't think Canada would risk it.
I hear you and I think that's part of the reason US folks are still being allowed up - but honestly, there's a pandemic on, Canada shouldn't be held responsible for making sure Trump doesn't look bad and end up flipping out unreasonably - that's America's problem.