What is one standard an author must meet to prove his authority as a writer?

One standard an author must meet to prove his authority as a writer is to demonstrate expertise and knowledge in their field. This can be accomplished by having specialized education, extensive research, and practical experience in the subject matter they write about. Authorities in a particular field are considered experts and are recognized as such by their peers and the broader community. Their knowledge and expertise enable them to provide accurate, reliable, and valuable insights in their writing.