There are webpages that have websites offering templates or themes for money (for Open Source content management systems). However, there are other webpages that offered these exact templates for free, most likely without permission from the original site. If a person unknowingly downloads those free templates, could the original company force the user to stop using it?
if i stole a bicycle and gave it to you, can the original owner demand it back when he see you riding it?
Are you sure that the free sites are the offending sites? Is it possible that someone took the free templates and then turned around to sell them? It is also possible that the terms under which they were purchased allows them to give them away (resell rights with no price stipulation).