The only time that “Do Not Duplicate” means anything is if a key is part of a registered master key system. A key can still be copied even if it states it shouldn’t be duplicated. However, if a key is patent-protected or a registered design, it’s illegal to duplicate it. Any key with a registered design is protected for 10 years and only locksmiths with the necessary permits can copy these keys. It’s often businesses or body corporate-run apartment complexes that have these types of keys. If you are unsure whether your key can be duplicated or if it is a registered key design, get in touch with a locksmith you trust.