Yes, the Maritime provinces have been doing it throughout the pandemic - sometimes even to each other, and both Quebec and Manitoba have had sporadic closures. Sometimes the restrictions are simply extended quarantines, but there have been cases of people being turned away at provincial borders. The constitutionality of it has been debated many times and will likely be the subject of court challenges long after Covid19 is in the rear-view mirror.A state can unilaterally close its border in Canada?
https://atlantic.ctvnews.ca/n-s-rei...kers-six-new-covid-19-cases-tuesday-1.5385412