I have only tried it on my own posts, so I am not sure
about thrid party cancels... I see no reason it shouldn't work.

To suggest fraudulently canceling message is irresponsible, and
contrary to EVERY Usenet providers Use Agreement. It will, or should,
get your Usenet account terminated.

This is possibly trivial, since there is some question whether any providers
still allow third party cancellations--except by the moderator of a
moderated group. My ISP does not appear to accept even first party
cancellations so I doubt they accept anything else.

Peter