The idea that Craigslist owns their posts is ridiculous. It may be true from a legal point of view, but from a moral point of view they're just the custodian of that data for the people posting it, and they should act as such.
This just puts you back where you started.
It's incredibly naive to assume you know best.
We have our job ads republished by job sites with user bases that are far outside what we're interested in, and it results in a massive waste of our time in filtering those candidates.