It's the law and it should be very strictly enforced because otherwise it'd open the door for the Middle East and North Africa... But I don't think Canada would want to join the EU, it's anti-Trump bluster.
Middle eastern or North African countries can’t join because the member states don’t want them to join and they need unanimous agreement. See Turkeys failed bid for example. Even a country with positive general public appeal like Ukraine is very unlikely to join in the next 10 years
Canada does not want to join the E.U. as a full member and that is not what is being offered.
Canada very much is not “blustering” when it comes to Trump. A big majority of Canadians see sovereignty and less reliance on the US as a massive issue. Canada has embraced China in a way that was unthinkable 5 years ago in a deal intended to hedge against the US. The Canadian Conservative Party lost an election it was thought to have a guaranteed win from and has continued losing seats since then in large part due to their half hearted response to Trump.
Turkey, only a tiny part of which is geographically in Europe, is a candidate (though talks are suspended in practice until, at least, Erdogan is out of power), and Cyprus is geographically in Asia/Middle East, not Europe. The rules could certainly be loosened further with agreement.
But also, yes, Canada probably does not want to be a full member, at least in the near-term; they want some sort of alignment not amounting to full membership. I wouldn't be totally amazed if we look back on this as the start of the (long-suggested) two speed EU system.