Do Laws Solve Anything?

Do laws solve problems? Do they cause more problems? I am not being facetious here, but I am truly looking for any instance of a law being passed that actually solved a problem. Not a problem caused by a previous law, (like "shall issue" concealed carry laws reducing crime rates), nor an authorization to punish someone for a crime. A case (or cases) where there was a real problem, and then a law was passed, and the problem was gone. Any ideas?