Why is Castillo executed in the novel, Midnight in Europe?

Castillo is coldly executed in Madrid not because he has committed any crimes, but simply because the inspecting officer notices that the lining in Castillo's coat has been torn. As the officer says: "'You seem to have tipped the lining of your coat. No, no, I am mistaken, the lining has been cut open.' He stared at Castillo, then said, 'Is there something you would like to tell me? To unburden yourself?'" before killing him.