How to restore Library and System Folders from Backup copy

I had to manually copy my MBP hard drive into my iMac as a backup (the MBP had a hard drive cable fault so I couldn't use TimeMachine). I reformatted the Hard drive and I've now moved the entire Hard drive copy back onto my MBP desktop. My problem is that I can't replace the new Library & System folders with my old versions. Every time I try, I get this message - " '......' can't be modified or deleted because it's required by OS X."

Is there a way to restore my old Library & System folders?