Canada, the draft, and the Smart Border Declaration

I’m not asking about any of the rumours regarding any candidates alleged secret plans to reinstate the draft. If the draft were reinstated based on laws enacted in 1971 college deferments would last from semester to a year. But articles also keep saying that fleeing to Canada won’t be an option either. I’ve read the the Smart Border Declration could be used to stop draft evaders but how exacltly? Do you need too check in with the US gov’t before leaving the country in addtion to Canadian Customs? What about the fact that most of the 49th parellel has no security and Customs stations are sometimes miles form the border? Can’t you just walk across the border in most places?