Oops I posted no but I ment yes, blah.
I would say it depends on the circumstances. Like if some one said a level/graphic/npc maker sucked and they didnt want his stuff anyways. Then they shouldn't be global banned since the person said they didnt want them. However in most circumstances it shouldn't be allowed. Otherwise any one any where could potentially ruin a server just because they decided they didnt want to work there anymore.
Personally I make it known that if a person quits or is fired at any time all work will remain on the server and the person who made it will not be able to remove it. Then there are backups having lots of back ups helps against this.
