I had no clue there are laws dictating that you can't ask how an employee was at a pervious job. Seems like a terrible idea to me. Is this a state by state basis?
As someone who has hired several people and been a manager for years we were always coached on exactly what you can and cannot ask when calling work history references. Hell a lot of companies just stopped calling them.
Like how can you even trust the words of a previous employer? You have to be able to determine if they are just being petty or are bitter etc. Like nothing prevents someone lying to you when you call. Regardless of whether the employee was amazing or not, gave notice etc the previous employer could easily just be upset and jealous and bitter.
No point in riskig yourself or company for a civil lawsuit over that shit