And here is a page from a 1817 law book which specifically says that Vattel was the source for "Citizen".
Let me once again provide the title and author of that book and page.
Judge Samuel Roberts, the Court of Common Pleas of Pennsylvania, was the sole author of the book, A Digest of Select British Statutes. There were no co-authors. The book is a recitation of British Statute Law by Judge Roberts.