Hi,
I have such access, and remove them once in a while, but unfortunately these accounts usually subscribe and then send 10 spams immediately - so I can remove them from the archive but it's too late for all the subscribers who will have already received them.
I'm not sure what to do about that :-( In the old days, I ran my own mailing list server (majordomo) and my own spam filtering tools, and had full control - but nowadays I can only hope that Google Groups does good spam filtering - which it usually does but not always :-(