Copying files from read-only media or an external drive (or even a network share) can cause them to become “protected” upon being written to disk under OS X. Problem is, when the urge to modify/rename the rises, You’ll end up getting an error message stating that it sure is protected and it should be left untouched! It is possible, however, to manually select the file(s), click on Info and un-tick the Protected box at the top of the info box. Doing this with 2-3 files is easy. Doing it to 30-40 is a real PITA! But fret not, as the solution to bulk-remove this permission setting is here:
Open your favorite Terminal app, navigate to the directory and issue the following command to remove this flag from all of the files within this directory:
chflags -R nouchg *
Now you are free to modify said files 🙂
Source of this solution is here!