A book published in 1875 is in the public domain.
A scan of it possibly being copyrightable in certain jurisdictions by "sweat of the brow" logic is not copyrightable in every jurisdiction.
But if there was a simple contract written and agreed to, that stated that the person being given a PDF or JPEG copy of the 1875 book was being given these files to do with what they wished, with the caveat being they couldn't reproduce them in whole or substantial part, or otherwise proliferate the scans to others (whether for free or profit, whether citing the scanning source or otherwise)...
Would that contract be able to stand up in a court of law (namely US), that while the images are of a book in the public domain, and not copyrightable by "sweat of the brow" and thus outside of copyright entirely, and in theory one could do with them whatever one wanted...if there was a contract whereby one person agreed NOT to exercise the right of public domain protection, is that valid?