well, if they don't recognize the succession then it remains in the eu as a part of spain.
and, if they do recognize the succession then it should follow that they remain in the eu, too.
i cannot imagine a scenario where the eu would recognize the succession, and yet deny entry. the political situation would have to dramatically deteriorate, to start.
https://www.thelocal.es/20171010/analysis-an-independent-catalonias-tricky-path-to-eu-membership
jagmeet singh must cut his beard.