At the time the Third Package was put together (early 1990s) which defined European liberalisation, three non-EU airlines were given ‘honorary’ Community Carrier status. One was SAS which at the time was only 2/7 owned by (Danish) EU interests – Sweden was then not an EU member. The others were Britannia and Monarch, both Canadian-owned.
Whether the EU would allow the rule to be bent in order to – for example – rescue a Central European national airline from extinction is a moot point.
Also, I’m not sure how they monitor it. I’m pretty sure BA has a substantial non-EU ownership base, maybe close to the limit, and shares are changing hands every day.