The US does not recognize copyrights over databases. The issue though is that depending on the ads in question there may be creative elements.
For example, suppose I place an ad to rent my house out and include just info. Not likely protected but if I do it in iambic pentameter, probably is protected.
What this wouldn't prevent is someone scraping CL for facts (appartments for rent, x bed, y bath, z sq ft), extracting those facts, and arranging them in another order. That doesn't strike me as protectable in the US, even if it involves scraping directly from CL.
For example, suppose I place an ad to rent my house out and include just info. Not likely protected but if I do it in iambic pentameter, probably is protected.
What this wouldn't prevent is someone scraping CL for facts (appartments for rent, x bed, y bath, z sq ft), extracting those facts, and arranging them in another order. That doesn't strike me as protectable in the US, even if it involves scraping directly from CL.