The Apple Time Machine service makes fairly nice backups using hard links and everything, but if you need to somehow modify the backups yourself to remove some obsolete files (which take up a lot of diskspace for example) you’re pretty much out of luck the normal way.

Removing the ACL’s and modifying the access rights with chmod has no effect whatsoever. You still end up with “Permission denied” from the shell or “The operation couldn’t be completed (OSStatus error -5000.) Insufficient access privileges for operation” from tools like Path Finder.

There is a way however to modify the files anyhow. Note that you can _seriously_ damage your Time Machine backups so only use this if you know what you’re doing!

If you have Path Finder installed it’s easy to do this graphically using this command:
[bash]sudo /System/Library/Extensions/TMSafetyNet.kext/Helpers/bypass /Applications/Path\ Finder.app/Contents/MacOS/Path\ Finder[/bash]

Alternatively you can just manipulate it through the shell:
[bash]sudo /System/Library/Extensions/TMSafetyNet.kext/Helpers/bypass rm -rifv /Volumes/[TimeMachineDisk]/Bcakups.backupdb/SomePath[/bash]