It would be a civil tort (If my terminology is correct) and reliant on someone to attempt to enforce their ownership. "Illegal" implies criminal infringement.

It would be a civil tort (If my terminology is correct) and reliant on someone to attempt to enforce their ownership. "Illegal" implies criminal infringement. And specifically in the case of YouTube, they are covered under the safe harbour provisions of the DMCA and if a claim is received against this video would proceed accordingly.