> The president of the European Commission has backed proposals for Canada to become the EU's first "associate member".

Article 238 of the original Treaty of Rome, which is now article 217 TFEU, provides for the EU (or its precursors) to enter into "association agreements" with non-member states, e.g. Turkey has one of them. Many current EU members (e.g. Greece) had them before becoming members.

A lot of 1970s/1980s sources referred to these states as "associate members of the EEC" – but it seems like everyone has forgotten that.