Anyone can sue anyone for anything. All it takes to have a lawsuit is to submit a filing fee to a court, and someone to serve the papers.
There are many lawsuits that are baseless. There are many lawsuits that are frivolous. If your instance is on the receiving end of one of these lawsuits you will have pay for a lawyer to defend yourself regardless of the merits of the case.
Courts don’t proactively decide whether someone can or cannot be sued.