While creating a zfs filesystem by a delegated user works fine, creating a zfs volume fails:


# zfs allow mypool
---- Permissions on mypool --------------------------------------------
Permission sets:
	@container clone,create,destroy,mount,mountpoint,promote,reservation,rollback,snapshot,volblocksize,volsize

# zfs create mypool/container
# zfs allow -u myuser @container mypool/container
# su myuser

$ zfs allow mypool/container
---- Permissions on mypool/container ----------------------------------
Local+Descendent permissions:
	user myuser @container
---- Permissions on mypool --------------------------------------------
Permission sets:
	@container clone,create,destroy,mount,mountpoint,promote,reservation,rollback,snapshot,volblocksize,volsize

$ zfs create -o mountpoint=legacy mypool/container/myfilesystem
$ zfs list -r mypool/container
NAME                            USED  AVAIL  REFER  MOUNTPOINT
mypool/container                192K  50,3G    96K  /mypool/container
mypool/container/myfilesystem    96K  50,3G    96K  legacy

$ zfs create -V 128m mypool/container/myvolume
cannot create 'mypool/container/myvolume': permission denied

From man 8 zfs delegating operations on volumes should be possible, no word is found that creation of volumes is exempt:

zfs allow filesystem|volume
     zfs allow [-ldug] user|group[,user|group]...
	 perm|@setname[,perm|@setname]... filesystem|volume
     zfs allow [-ld] -e|everyone perm|@setname[,perm|@setname]...
	 filesystem|volume
     zfs allow -c perm|@setname[,perm|@setname]... filesystem|volume
     zfs allow -s @setname perm|@setname[,perm|@setname]... filesystem|volume