I think what it tells employers, who don't know better, is that the person is a Certified Information Systems Security Professional, and they might have heard all government security employees must have one, so it must mean that the people are extremely skilled. In this, I'm not qualified to say but my hunch is, not very likely based on a few untechnical people I know in the last few years who passed the test successfully.
What it should tell employers however is that the person is capable of critical thought and has a light familiarity with a wide range of security concepts.
Why should I have to pay a pretty significant amount of money at the start of my career to buy a piece of paper that suggests I'm capable of critical thought? In fact: isn't doing the exact opposite of that actually doing a better job of demonstrating critical thinking skills?
What it should tell employers however is that the person is capable of critical thought and has a light familiarity with a wide range of security concepts.