There is a secutiry vinyl that when peeled breaks into small pieces but even that can be dealt with, I don't think there really is anything to stop something from being peeled off and if there was you could just wipe laquer thinner or vinyl thinner across it removing any graphic information that was printed be it by screening solvent or thermal. I think thats when companies get a metal plate stamped / printed with info and riveted on to the product
I've seen products for the Gerber Edge made for this purpose. Graphic Marking Systems (www.graphicms.com) sells this stuff.