I am a non-root user, and have made a directory into which other users in my group can write. The directory is setgid, so files and directories within it have the same group.

I can delete files placed into this directory, but if a user creates a subdirectory with files in it, I can't seem to delete those. Is there something special I can do (other than, say, bothering the user in question or the sysadmin about it) to get rid of this subdirectory?