If the copying is fair for the purposes of research or private study, or for the purposes of criticism or review, no permission is needed but an attribution is. Criticism or review is the most likely, but some parts of a thesis may just be for the purpose of exposition of stuff already known.
Easiest thing to do is gently put tho boot into the research underlying the thing they want to copy, alternatively praise it in some way. Or both. Criticism and review innit.
More seriously, take a self critical view of why the thing is being copied. Is it just to save the faff of diy or necessary to make a pount?