Stays blond permanently? That’s peculiar. I imagine it could turn hair blonde, but overtime as hair cycles, I would think brown hair would grow back. Sun destroys melanin in the hair follicle, which would render laser completely ineffective. My guess is that even if your root happened to be dark (you could probably tweeze out a hair to see if the root is dark), laser won’t work. Think about it this way: before treatment you shave the hair. When you fire the laser, the laser is attracted to the pigment of the hair that’s just sticking out of the skin. That energy then travels down the hair shaft to the root. If you have blond hair, it won’t be able to detect the pigment to travel down the hair shaft. At least that’s my guess on why it wouldn’t work. Now maybe if you shave the hair, and then you can see dark spots from the root, then laser could possibly work in that case. That’s just my theory for why it may/may not work.