I'll be honest I never though anyone would think whether Raheem Sterling is going to be allowed to work in Spain was an actual issue.
The conversation is would Real Madrid try sign him given the 3 non-EU spots are full, and the Kolpak agreement means he doesn't count as a non-Eu player, so problem solved.
I'll leave this here and you can decide for yourself if Sterling's going to meet the very strict requirements of more than 1 year work contract, wages above ~€90,000? (1.5x average professional) and 5 years experience in his field
Check if you need a visa or permit to work in Spain and how to get one if you do.
www.gov.uk