I was told by the installer of my last flooring that there was a local law that said you cannot have more than 2 layers. I wondered why and still have not gotten an answer. Is there anyone that if this could be true and why?

I am unaware of any codes that address this but some manufacturers may have do's and donts's about what is under their vinyl. I would think any old cushionbacked tile or sheet would have to be removed first.