Not a bug, working as intended. Entering a country that you aren't a citizen of isn't some inalienable human right, especially if you're a convicted criminal.
Well, yeah, entering the US as a non-citizen is a privilege granted at the discretion of the US federal government. Border control is an essential function of a sovereign state.
>I also find it a bit disturbing how easily you apply law & order in the name of a country that was not involved in deciding the validity of that decision or the circumstances behind it.
It's disturbing to not want criminal elements freely entering your country? If they're a not refugee and they can't follow the law in their country of origin, why should any other country be obligated to let them in?
If the Canadian border authorities are searching your person, such that they are likely to notice something like a concealed carry permit, your border crossing has already gone south.