tinting your winshield

Me and my friend both got our windows tinted toghether like 3 months ago. He has the 2000 escalade. We did 20% all around. Yesterday he got his indshiel tinted. It looks so phat. I really wanna do it. I already have my 2 front driver and passenger windows tinted but I heard it's like the most illegal thing ever to tint your winshield. Is this true and should I do it??