Not copyists but lawyers — the people who knew what the text said and what it required.
A scribe in the New Testament is a professional interpreter of the law, which is why some translations render the word "lawyer" and others "teacher of the law". The job began with writing — Ezra is described as a skilled scribe in the law of Moses — and grew into the authority on what was written. They are usually named alongside the Pharisees, though the two are not the same thing: scribe is a profession, Pharisee a party, and a man could be either or both.