Let that happen for long and you'll quickly have thousands of workers who need to feed their families converging in the blockade to take matters into their own hands.

It's not just the immediate impact, either. Canadian manufacturers who sell to the U.S. (which is pretty much all of them) are constantly fighting against 'buy American' legislation that makes it more likely companies will shift production out of Ontario - and trade disruptions make it even harder to compete if Canada looks like a flaky trading partner that can't even keep its own border open. And manufacturing workers know what's at stake, and things would get ugly quickly.

So it's not just inconveniencing corporations - it's threatening the short and long term viability of tend of thousands of jobs and the people working those jobs aren't likely to take it laying down.

So blocking trade isn't off the table, but anyone who does it had better expect the government to treat it as a public order emergency because if they don't, it will very quickly become a public order emergency on its own.