Copyright ownership of articles written for your magazine

One of my excellent contributors has been approached with a view to having his columns made into a book and published. He may even have his work dramatised too. Who owns the copyright? The author? The Parish magazine for which they were written? The church ( in our case this would be the same as the magazine)?
The question that occurs to me is, "Why are you asking?" In a spirit of generosity surely you will be delighted if the author receives royalties. He might even give some to the church. Unless he is intending to claim retrospective royalties from you surely anything is likely to just produce unnecessary friction which might appear to arise from greed.