Once they're convicted, they won't be welcome in Canada.
A few years back, they were turning back people with 30 year old pleas to minor possession charges on the grounds that they were convicted drug criminals.
This is pretty much the same for Canadians going to the US. And if anything US border has become even more difficult. I know people who live in border cities (e.g.Windsor/Detroit and Tsawassen/Point Roberts on the west coast). There has been a culture of border crossing, especially for Canadians crossing to buy stuff cheaper in the US, like gas. In the last 10 years it has become waaaay more difficult to cross into the US.
