If you manually extract something and create a broken signature in the process, Gatekeeper helps you out by refusing to open the bundle in ANY application, and

If you manually extract something and create a broken signature in the process, Gatekeeper helps you out by refusing to open the bundle in ANY application, and instead simply stating that the file is corrupt and should be deleted. I've hit these things often enough that I just turned it off. Gatekeeper doesn't protect against unsigned code execution; it's merely the same old quarantine code with code signing bolted on. It prevents you from stupidly double clicking an evil executable -- in theory.