The provinces can regulate travel within their provinces. Many have that in their public health act as an emergency power that can be done in a public health emergency. Many have it in their emergencies act provincially, but there does seem to be this reticence among some to use it.
For example, B.C. really was concerned about using it to keep Albertans out, so there seems to be.... Once that Albertan is in B.C., then they have the power, potentially, to exclude them, but there seems to be some concern about the legality of that, whereas with the federal government, I think there wouldn't be that same concern, because there's no question that they could do it federally.
I think there are problems with the variants moving from one province to the other. We had a situation in Alberta where one traveller came from B.C. to Alberta. There were 35 cases, at least one death and two ICU admissions, so these provincial borders pose real threats.