Instead of banning ghost job ads, job board companies like Indeed should consider "authentic job" badges for ads and require proof a person was hired to the position. When you have real, authentic jobs people gravitate to your site. If you let junk job ads (ghost or otherwise) run amok on your site, everyone leaves. This is why you don't hear about monster.com anymore.

You don't need another government ban. Let capitalism do its job.

Again, you need to deal with people gaming the system - claiming they were hired in order to boost credibility ranking of the company (or site).

When there’s a benefit to the site and the employer, that’s two potential sources of corruption.