I don't think that there are any. Simply writing a program that outputs sounds that resemble someone's voice can't be illegal, right? You can use it in illegal ways, sure, but I don't think there are any laws concerning software like this.
As I said, they lost on copyright claims but these cases involved their natural voice. If the voice was a made up voice, such as a character an animated character, I wouldn't immediately dismiss the idea that it might be copyrightable.
Tangentially related, if you have your voice print as a security mechanism at a financial institution (Vanguard), you should ask them to turn that off.