In some cases you will indeed have to prepare a few documents before you can start an assignment.
Some guidelines include contracts or image rights authorization documents, which must be printed in several copies beforehand and signed at the time of the assignment. This is a completely standard process.
If people are recognizable in the photos, it is essential that they sign an image rights authorization document.
If nothing is indicated in the guideline or in client comments, it is because there is no document to be printed or signed.
This is why we insist that the guideline is read carefully and adhered to. By doing so, you will more easily avoid any litigious situations. On allocation to an assignment, you must confirm that you have read this guideline.