assuming the foil strip was on the disc and not on the dvd case. . . .you will find this funny. . . . they are supposed to be copy protection for VHS video cassettes not DVDs
it is in case someone tried to physically open a VHS and replace the film with a copy. the metal foil will show that it was cut or peeled off meaning tampering was done.
whatever idiot put it on a DVD was too stupid to know this apparently. i know for sure it is not for the metal detectors. those would cause imbalance of your dvd disc and cause damage to your dvd player.
Prelude2244 i suggest peel off the strip and use a product called "goo gone" to wipe off the sticky mess. the risk of imbalanced disc is not great, but dont play those discs for too long.